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A war for Immunity has been waged

A formula has been created. One that will ensure immunity for all. But it’s been stolen as a hidden enemy undermines every step to save the Vulnerables. Echo is doing everything she can to hunt the saboteur. River is about to discover he’s more connected to this than he ever thought possible.

As they both learn they can’t escape their roots, the people of the Dead Zone make it clear they’re no longer willing to be cast aside. Immunity should be granted to all, not just the selected few. An uprising is inevitable. And the wealthy inhabitants of the Green Zone are determined to end it before it begins.

Echo and River will have to choose between love and loyalty. Because the race to find the formula has begun. And the fate of humanity depends on their success.

276 pages, Kindle Edition

Published August 25, 2023

90 people are currently reading
238 people want to read

About the author

Tamar Sloan

141 books431 followers
Tamar really struggled writing this bio, in part because it’s in third person, but mostly because she hasn’t decided whether she’s primarily a psychologist who loves writing, or a writer with a lifelong fascination with psychology.

She must have been someone pretty awesome in a previous life (past life regression indicated a Care Bear), because she gets to do both. Beginning her career as a youth worker, then a secondary school teacher, before becoming a school psychologist, Tamar helps children and teens to live and thrive despite life’s hurdles like loss, relationship difficulties, mental health issues, and trauma.

As lover of reading, inspired by books that sparked beautiful movies in her head, Tamar loves to write young adult romance. To be honest, it was probably inevitable that her knowledge and love of literature would translate into writing emotion driven stories of finding life and love beyond our comfort zones. You can find out more about Tamar’s books at www.tamarsloan.com

A lifetime consumer of knowledge, Tamar holds degrees in Applied Science, Education and Psychology. When not reading, writing or working with teens, Tamar can be found with her husband and two children enjoying country life on their small slice of the Australian bush.
The driving force for all of Tamar’s writing is sharing and connecting. In truth, connecting with others is why she writes. She loves to hear from readers and fellow writers. Find her on all the usual social media channels or her website.

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5 stars
160 (45%)
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51 (14%)
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Displaying 1 - 30 of 31 reviews
Profile Image for Jessica.
1,154 reviews29 followers
July 6, 2023
The hunt for the Sovereign and the code they need to make a formula for immunity is still on, and this book takes off exactly where the previous ended.

When people get desperate it's easy to let your emotions control your actions instead of logic. There's disagreement between our friends, and River is pulled between Echo and Flora. Echo is certain that Flora is hiding something, but River trusts his sister blindly. The question is, who's right? I can't wait to read the last book in the series!

* I received an ARC from the authors and I'm giving my honest review. *
Profile Image for Devika.
700 reviews20 followers
June 15, 2023
Venom Rising is the fourth part in The Sovereign Code series. This series is a really good series so far and I really enjoy reading it. The storyline is just really unique and these books all read so smooth. What will this part bring to its readers?

Find out in my review on my blog Boekensteeg
Profile Image for Christine Cazeneuve.
1,462 reviews40 followers
May 18, 2023
The saga continues

I'll admit that I couldn't wait for this to be released and will eagerly be awaiting the finale to the series. However, this was my least favorite of the group. It just didn't have the same level of action as the prior two and I found myself getting a little bored. It wasn't until the last 10% that it really got back to its roots so I am hoping the last book will be the best!
2,996 reviews43 followers
June 20, 2023
This is book four of The Sovereign Code series and starts with Echo and River struggling in the Extinction Zone, on their last legs, until they come across a broken down tower, similar to the Sting. They are too tired to check all the levels of the building, having had no water or food, so fall asleep on the floor, only to be awoken by armed strangers. They are now apparently in the Moon Zone, amongst the Moon Workers, who believe night is safe and tend to their plants only at night, when they can’t even really see what they are doing! Once they find out Echo and River have been Forgotten, as they call those kicked out of the main zones, the Green Zone and the Dead Zone, they accept them and give them new names. They also have a pictorial history of the zones and the attempts to feed all and how they have failed in the past. The Immune and those in the Green Zone are never hungry, whilst those in the Dead Zone are left to starve and fall ill, terrified about being stung by a bee as its sting is deadly.

They have been trying to find the Sovereign and the people of the Dead Zone are getting tired of being left with nothing and are now being punished and their rations cut completely. They are ready to rise up and want Immunity for all, not just the wealthy and privileged of the Green Zone, who have always lived an easy life. There is lots of hate between the two groups and neither knew anything about the Moon Workers. Families are split apart every time people are tested for their immunity. Chase who is Dead Born and River’s twin sister Flora, who was Green Born, are a strange pairing, with Chase leading the Razzers, the group fighting for equality and raiding the other zone for food for their people. Who River and Echo can really trust is questionable, with many they are in contact with showing different sides of themselves, depending on who they are interacting with. Echo and River were thought to be dead by everyone else and need to hide when they return, with Flora making a safe haven and new lab with her mechanical worker bee, Nectar. Oren is still in charge and wants to destroy all of those in the Dead Zone. He is still a danger to one and all, even putting his own children in the firing zone.

Some hidden secrets are revealed about family and others, but betrayal hits hard yet again and brings new dangers to the group and surprises they never thought would happen. It is a race to a solution, as loyalty is tested and some are found lacking. The only ones Echo and River can trust are each other. They have one more person they want to test as the Sovereign, but Echo soon figures out a different reason for the list of people tested so far. Even her own immunity to a queen bee sting is put into question. Even if someone has sacrificed or helped them in the past, it doesn’t mean they can be trusted now. With Oren’s wide reach, anyone can be turned and it looks like the series is about to end in an explosive manner, with shocks aplenty. I can’t wait to read the last book to see who manages to survive and if they can actually solve the matter of immunity once and for all, or if thousands are doomed to die painfully! So many twists and turns, as people change allegiance at the flip of a coin, and the danger ramps up into impossible situations. I received an ARC copy of this book from BookSprout and I have freely given my own opinion of the book above.
Profile Image for Katheyer.
1,557 reviews25 followers
May 14, 2023
Prepare yourself for a wild and intense ride, this book takes on exactly where the previous let us…. With Echo and River just been dumped in the Extinction Zone, a death sentence should they not be able to find shelter, and shelter they will find eventually, only to learn that there is a lot more to being alive that just to be able to survive. This is a pivotal book in the series, in which Echo and River will find new allies, and confront new enemies, while finding out that utopia and real solutions are not always one and the same. A wonderful ride from start to end, perfectly paving the way for the upcoming and final book in the series.

Sloan & Catherine’s wonderful dystopian world, foreign yet familiar, beautiful, and terrifying captivates the reader at first read. Their fluid and nuanced writing conveys a powerful message, whose actuality plainly apparent. The extraordinary thoroughly built-world is populated by well developed and multifaceted characters, credible and relatable at all times. YA fast-paced story, which provides action non-stop, an intelligent plot, and very satisfactory developments, a real page-turner, a great adventure that leaves a lasting impression without disregarding the level of pure entertainment every good story should provide. Beware though of some ‘side-effects’ as sleep-hours lost (should you start the book in the evening) and a brand-new appreciation for honey 😉

Sloan & Catherine dystopia effortlessly surpasses YA classical works as “The Hunger Games” and “Divergent”, offering not just very carefully crafted worlds, the right balance between dystopia and social critique, with a constant questioning of the values and drawbacks of the systems they create, allowing the reader to understand its strengths and flaws and find unsettling similarities to our own society and values. “The Sovereign Code” series offers a brand-new dystopian world, and already at midpoint in the series it is the perfect and sole contender to an ex-quo place as the best dystopian verse of this decade together with their widely recognized “The Thaw Verse”.

Profile Image for Reads_Must .
959 reviews13 followers
May 9, 2023
Venom Rising
The Sovereign Code #4
YA, Dystopian
Heidi Catherine & Tamar Sloan
⭐️⭐️⭐️⭐️⭐️

Whenever I get an email saying there is another ARC available for this series, I get so excited!

I think this book was the best one yet! I loved returning to the world these are set in, especially because this time, Echo and River are exploring places they've never been to or heard of before.

The other survivors that they found were very interesting, and very odd 😂. Heidi Catherine and Tamar Sloan did a great job of making them seem slightly unhinged but I felt sorry for them at the same time. I'd like to see more exploration to see what things are like elsewhere.

The pacing was great. I flew through this book and not once did I feel like it dragged. I was surprised everytime I checked how many pages I had left.

There were some plot twists that were very well done and I liked the almost constant back and forth of "we can trust this character.....no we can't....yes we can". It made me curious about ulterior motives and what might happen next.

The ending was great, there's impending danger and betrayal and now I can't wait to read the next book!

*Thank you to @Heidicatherine and @Tamarsloan and for providing this ARC. This is my own opinion and an honest review, which I am leaving voluntarily*
Profile Image for alishasbooknook.
195 reviews2 followers
October 24, 2024
The fourth book of The Sovereign Code was absolutely incredible! From the moment I started it I was drawn into a richly created world that blends dystopian, action, romance and suspense seamlessly.

The intricate details and immersive settings really allow you to escape into a realm that feels both familiar and futuristic, the authors abilities to create such vivid imagery is amazing.

I loved Echo and River again, which isn’t surprising😂 I again didn’t like Chase, he’s starting to just annoy me now and I don’t know how I feel about Flora anymore. I’ll have to see what happens in the last book.

For the characters I actually do like, I found myself empathising with their journeys, feeling their pain and joy as they fought challenge after challenge.

The pacing was right back to normal and kept me on the edge of my seat, I couldn’t wait to see what happened next and with the ending I need to know what happens now. I can’t wait, I’m too impatient 😂

Overall, Venom Rising is an incredible and thought provoking read that I definitely recommend.
Profile Image for Avo_in_bookland (Narelle) .
121 reviews4 followers
November 20, 2024

Book 4 in the Sovereign Series sees the hunt for the Sovereign and the code continues. An Uprising is inevitable as the people of the dead zone won’t tolerate being starved and ignored anymore. Immunity for all but not if the Green Zone have it their way.

We see our beloved favourites being torn between a rock and a hard place as characters start to act on emotion not intelligence. River finds himself stuck in the middle as Echo Accuses Flora of hiding things but River trusts his sister Completely.

Plenty of new characters as Echo and River find themselves in the Extinction Zone. And Found Family as they rescue from the Hive and secrets are uncovered. Will they find Rivers Mother?

I’m still thoroughly enjoying this series. It’s a very unique concept and fast paced which I like. I love the use of the Worker Bee Nectar and all the unique characters. Some you just adore and others you certainly love to hate. Looking forward to book 5 to see how the Story Ends.
1,221 reviews15 followers
July 10, 2025
With Survival on the Line, Who Can You Trust?
Echo and River are on a desperate mission to recover the stolen formula that could cure bee venom and save humanity. But with enemies hiding in plain sight, nothing is as it seems. This installment takes readers on a dark, twist-filled journey where trust is dangerous—and betrayal could be fatal.
As tensions rise and loyalties are tested, the stakes couldn’t be higher. Will Echo and River survive the deadly forces closing in around them? Or will their fight end in heartbreak?
This cliffhanger will leave you breathless—and hungry for the final book. If you're new to the series, start from the beginning to fully appreciate the journey. The end is coming, and every page counts.
Profile Image for DeeDeeWReads.
1,157 reviews16 followers
July 1, 2023
Another action packed book. River and Echo are continuing to look for the Sovereign. Who is it? Could they be mistaken to who it is? What will they do when they find out? IS there a Sovereign to find at all? The questions keep coming, and sometimes answers can make it all more confusing.

I enjoyed this 4th book of the series, we have 1 left, the Finale, the end or the beginning of an Immune life, that we don't know.

Great read for those that love dsytopian novels, which are some of my favorites!!.

I received a free copy of this book via Booksprout and am voluntarily leaving a review.
Profile Image for Patricia.
610 reviews1 follower
May 24, 2023
What to say about this, the fourth book in the Sovereign Code series. It is a roller-coaster ride right from the beginning. New friends and new enemies. Twists and turns with surprises and betrayals. Can River and Echo actually trust anyone? I found myself holding my breath during parts of the book wondering what would happen next. A warning for other readers, it ends in a cliffhanger.
Really one of the best dystopian series I've read.

I received a free copy of this book via Booksprout and am voluntarily leaving a review.
Profile Image for Debbie Eyre.
5,893 reviews116 followers
June 6, 2023
This series is incredible and this latest addition only enhances that. Echo & River’s journey to help civilisation carries on but continues to be thwarted by corrupt people who are trying to hide the immunity cure and only let a select few have it instead of everyone. This dystopian style read is gripping and enthralling as more twists and surprises are thrown our way, there’s betrayal, there’s deceit & lies and there’s more drama, intrigue and suspense and I have to say I was on the edge of my seat. I am so looking forward to the next book.
960 reviews
June 3, 2023
Echo and River struggle more with each day passing.
Their fight to find the cure, to save humanity, is doubled with their fight for their love.
From the beginning, they were total opposites.
And they are at the moment when this may be important for them and their relationship.
What the last book will bring?.

I received a free copy of this book via Booksprout and am voluntarily leaving a review.
Profile Image for Sam.
2,550 reviews41 followers
May 16, 2023
A really beautifully written story in this amazing dystopian series! I loved everything about this! The characters are balanced & well thought out, good levels of tension & pace all through the story, brilliant ideas, so well done! A few twists & turns, completely not expected! A really amazing experience! I do strongly recommend!
Profile Image for Jessica Fuller.
410 reviews79 followers
January 11, 2024
Excuse me but this book was insanely good!
I’ve loved all the books so far but this one has me in the biggest chokehold. I am obsessed. The twists, the shocks, the characters, the ending. Chef’s kiss 👌 I am getting stuck into the last book as soon as I can. I will recommend this series until my dying day, I swear. 🙌
4 reviews
March 14, 2024
Best one so far

I've mostly continued this series out of curiosity. The previous books are unique and moderately interesting, but not very well written. This one was much better than its predecessors, and I really hope these authors continue to improve their execution, because they have good ideas.
Profile Image for Victoria Weir.
74 reviews
June 12, 2024
Venom Rising ✅

Another amazing read.
I’m constantly blown away by how small these books are but how much the authors seem to be able to cram into each book.

So many truths uncovered this book and some many loose ends to tie up next book!

Who’s on the good team and whose not. Will they defeat Oren?

I am so excited to see what the authors do to wrap up this series!
Profile Image for Denise.
395 reviews
April 3, 2025
a predictable visit to extinction zone and another group of survivors. is there a formula that says it's needed plot line to go way out and find a new group of survivors who are wacko?

I feel 70% of my lower scores for the series is due to the narrator who does whiny voices and several times voices are no longer distinct
This entire review has been hidden because of spoilers.
Profile Image for Jill Gauger.
1,226 reviews11 followers
May 12, 2023
Twists and turns, betrayal galore. The non stop action keeps you on your toes and your head spinning. I loved this book and series to date but the cliffhanger has you wanting the next book immediately if not sooner. I am craving more now.
Profile Image for Shayay.
2,797 reviews54 followers
May 21, 2023
Entertaining fourth book! Echo and River continue their struggle to survive in a dystopian world; trying to find a way to immune everyone and dealing with corrupt individuals causing problems, all of it can be a dangerous endeavor. These two continue to persevere. Looking forward to the finale!
Profile Image for Sherry.
274 reviews1 follower
June 27, 2023
Wow! This book is crazy! So many reveals! And who are the good guys and who are the bad guys here?!?! The plot twists are mind boggling. The ending is unreal 😳! I have absolutely no idea where this story is going now! I love it!
Profile Image for Lulu.
362 reviews
November 1, 2023
This is very frustrating. Little things the reader figured out several books ago are barely being revealed like some big gasping moment that they're not. I got bored of the book because of the predictability. I really wanted to love the characters but found myself annoyed with them instead.
Profile Image for Kimberly.
1,144 reviews40 followers
November 10, 2023
Wow, just wow

Boy, did this book have tons of twists and turns! It was so good and I couldn't believe where it went in this book. And what a cliffhanger to this one. I am off to see how it all ends for Echo & River!
Profile Image for William Vegvari.
404 reviews5 followers
May 11, 2023
I've enjoyed this series from the start and it just keeps you reading to see what happens next.
A real page turner that will not let you go.

Highly Recommended
Profile Image for Helen Jones hazlewood.
35 reviews1 follower
May 29, 2023
Wow, what a great read this was! So many unexpected twists, so much tension and a real cliffhanger....I can't wait for the next one in the series!
39 reviews
June 20, 2023
Twists and turns


Definitely exciting turn of events With echo and river Still searching for answers. Flora and chase along for the ride big surprises up ahead

87 reviews
Read
October 18, 2023
Good

It was a very, very good book. I will have to read the next one to find out how it ends.
Profile Image for ems_booknook.
445 reviews19 followers
June 15, 2024
I finished this one yesterday and was so invested that I jumped immediately to the next one and didn’t even review this one.

I think that says it all.
Profile Image for Megan.
74 reviews
February 25, 2025
This one was probably my least favorite. It was pretty boring until the last 20% of the book. I still lo e the story and can't wait to see how it ends.
Profile Image for Rebecca Bean.
57 reviews3 followers
December 8, 2025
I was pretty consistently sucked in to this one. Some twists I saw a mile away. Others surprised me. Still frustrated by some characters, but I believe it's generally intended.
Displaying 1 - 30 of 31 reviews

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