Infernal Hearts

by K.L. Andersen

“I need you, Firefly. You’re my infernal heart, and without you, I’m nothing and have no purpose roaming between the two worlds.”

When humans have no idea the paranormal exists until one day the Demon King decides it’s time to come out from the other side of the Veil. But he has a purpose, and his eye is on one particular human woman.

And he’s been keeping a secret from her.

Will the secret he’s keeping drive her away when she finds out? Or will things get shaken up when there’s trouble with the Human Only group that seems to have popped up?


Infernal Hearts is the 1st book in a new series following the mates in the city of Mount Hellfire. 18+ materials
A happy ending is guaranteed. Please check the trigger warnings at the beginning of the book or visit the author's website for more information.

326 pages, Kindle Edition

Published August 13, 2025

About the author

K.L. ANDERSEN is a multi-genre romance author and avid reader. Whether it’s heart-wrenching or silly, she likes to write and dream up different worlds and the not-so-human men in them. She is a fierce Scorpio who lives in the Northern Midwest with her husband, two kids, two dogs, two cats, a bearded dragon, and the many chickens who roam around her home.

You can find her being a goober while enjoying writing, reading, gaming, or hanging out with those she loves.

Reviews

[Tonika · Rating 4 out of 5]

Teagan has a hard time making friends, and her parents have decided to take a new job and uproot her from everything she knew.

Fin, the MMC, who is boy next door material.

Viv, Teagans best friend since high school. Go through upheaval after upheaval.

I was Teagan in high school, and so when she cried I cried, I don’t know how else to explain it. The first 25% of the book is watching Teagan grow up between the age of 14/15 to the current time of 30.

And when Teagan returns home at 30 the demons come out of the closet.

The only thing negative I can say are the the very blatant slap you in the face clue that Teagan is so unaware of. Large red flags waving and she is so far in her own head she misses them all red flags, green flags. Seriously unless the information comes barreling down upon her. But she is not doing it to be stubborn or naive, she is just in her head with self down, self confidence issues, and trying to do good by being a good person, giving everyone chances.

The books also feels a bit choppy when we are going years ahead, although, I do understand, it can be hard to find a flow when the flow jumps a few years here and there.

I absolutely Love with Teags and Fin, they are adorable.

Key points in no particular order:
- Young (teenager) curvy FMC
- moving mid school year
- crochet
- Demon coming out of the veil
- Dub/Con woke up to heavy petting
- Tail play
- Attempted SA
- PA
- Kidnapping
- HEA but will it last!

[In her quiet lines · Rating 4 out of 5]

In Mount Hellfire, a city where humans have no idea the paranormal exists, everything changes when the Demon King decides to cross the Veil and reveal himself — with a very specific goal and his eyes set on one particular human woman.

That woman is Teags, a quiet young woman who, as a teenager, moved to Mount Hellfire with her parents. Soon after arriving, she meets Finn, the neighbors’ eldest son, and from the very first day their connection is instant and unbreakable. They spend every day together… until Finn’s 18th birthday, when, after confessing their love, he mysteriously disappears.

Thirteen years later, Teags returns to the town that broke her heart — and finds everything seemingly the same. But unexpectedly, the supernatural enters her life, bringing secrets and revelations that could change everything she thought she knew about the past and about herself.

My thoughts:
I absolutely loved Teags and Finn’s story — the mix of heartfelt romance, thrilling paranormal elements, and the sizzling, steamy scenes between them made this book impossible to put down. It’s emotional, addictive, and leaves you desperate for the next installment.

Favourite quote:
"I need you, Firefly. You're my infernal heart and without you I'm nothing and have no purpose roaming between the two worlds."

[Samantha Bennett · Rating 5 out of 5]

If you are looking for a good demon book then look no further! I had the pleasure of arc reading this book and instantly fell in love with it!
When Teagan moves to Mount Hellfire she meets Finn and they instantly become friends. Finn is always around and includes Teags in everything he does. The night before his eighteenth birthday she finally decides to tell him how she feels. But when she wakes up the next morning her heart shatters when she discovers Finn and his family have up and moved away. After many years of not so great dates and living in the city she decided to move back home and open up her bookstore next to her best friend Viv’s coffee shop. A town festival is cut short and everyone learns that there are other supernatural beings that live just beyond the veil and our government has allowed them to cross over to our world. Teagan is of course excites because she’s always wished something like this were true. She meets the demon king and is instantly drawn to him. But our king has a secret he’s keeping from Teags. Will she forgive him once she finds out? The only way for you to find out is to read this book!
I loved this book and it was my first demon book to read. It’s so well written and I love the storyline itself. My heart broke for our girl, but that heartbreak didn’t last long. I can’t wait to read the second book and learn more about Viv!!

[Shell · Rating 5 out of 5]

This was a quick enjoyable read. After finn was introduced I questioned his kindness, thinking of teenage boys and their wants and it could have gone either way especially once Misty entered the picture. I was happily surprised with his manner in handling that situation and respecting Misty's feelings even though it crushed Teagan at first. I think it gave good insight into the man Teagan would fall in love with. I had a few moments of laughter, tears and anger which typically makes me love a book even more. I received this book as an ARC for a free and honest review and entirely based on my opinion.

[PrettyLadyMaine Writes · Rating 5 out of 5]

I didn’t want this book to end. Teagan wasn’t good at making friends her and her parents ended up moving next door to the popular boy Finn and his family. Teagan and Finn fall in love but once he turn 18 his parents move them away so years go by before he sees Teagan again. When they finally reunite he changed he is no longer human but a demon their bond is as strong as ever. Teagan learns supernatural beings live in her city and Finn is the king of them all. I am so happy to receive this book as an ARC I am happy Viv gets her own story I can’t wait to read her book.

P.S please come up with character art I would love to see everyone.

[Shawn Burt · Rating 5 out of 5]

This book was so cute. The FMC is a teenager that moves to town, she is a shy book nerd that loves to crochet. She hates having to start over making new friends. That is until she meets her next door neighbor that just happens to be a hunk of a guy. He becomes her best friend, even though she is secretly in love with him. Until one night there is an exchange of gifts and more and her heart gets shattered. If you want to know more you will need to read the book. This is a really good book with just the right amount of spice and inhuman beings.

[Shannon Katariana · Rating 4 out of 5]

What can I say about this book? Hmm. I gave it a 4.5/5.
The characters and their growth is seen throughout the book.
The spice level is a good amount. Not to much and not to little.
The plot consists of Teagan and Finn as the main characters. You start off with Teagan moving to Mount Hellfire at a younger age. This is where she meets her neighbor Finn. From there you see their relationship and friendship blossom. Then after Finn’s 18th birthday everything changes. You will need to read to find out all the rest.

[Bookish_Nurse23 · Rating 5 out of 5]

ARC Review
5⭐️
I devoured this book in one day. I don’t typically read monster romance books but when I saw crochet hooks and yarn on the cover I was intrigued. I love to crochet! This story was the perfect balance of romance, comedy, and action. Many love-filled quotes to make any girl swoon. Top tier spicy scenes with no weird terms used. Super excited to continue this series. I don’t know if I could be called a monster romance lover but this book may have converted me.

[Lisa Meyeraan · Rating 5 out of 5]

Amazing story. love love love the characters.

I am so excited to see where the stories go for the rest of the series with all the different ways things have been set up in this book for future books.

Finn & Teags love story is so heartwarming. and Viv is definitely someone I want for my best friend.

love all the different inclusions of "in-human" characters. very fun other worldly book. so excited for more in this series 😍

[Bethany Latronica · Rating 5 out of 5]

I absolutely loved every moment of reading this book. The main characters are so fun and full of life. I adored them and their storyline. The FMC is resilient, strong, and funny with her quick wit - she's everything I love in a main character. The MMC is truly one of my favorites to date. From the first moment he was introduced, I knew he'd win me over, and he only gets better with time. 😏 The storyline & plot were incredibly unique, with a few twists I didn't see coming. I LOVE when a book pulls me in from page 1, and this one did exactly that!

[Kerrie Porter · Rating 5 out of 5]

This book was an amazing read. It takes you on a bunch of different emotional rollercoasters while reading the story of Teagan and Finn. The plot was perfect the spice was amazing and the plot twists were in the right spot and will have you wanting to keep reading to find out what happens next. If you like fantasy and a baddie fmc who is trying to find her way around life and the super natural world and people this book is def for you.

[Mala · Rating 4 out of 5]

This one borders from 3.5/4 ⭐️’s
the spice was 🌶️

While i enjoyed the story I just wished it flowed a bit better. It felt a bit rushed and too many plot ideas at times. I was a big fan of her first duet so I was hoping for the same pull from this one, unfortunately it juts missed the mark of keeping me obsessed. Over all a decent read.

[Stephanie Bennett · Rating 5 out of 5]

The Demon King calls her Firefly!
A paranormal romance that made me laugh and swoon and kept me so intrigued in wanting to keep reading to see how it all comes together and ends. I really enjoyed this book. The story and plot was like nothing I’ve read before. Great twists and turns to keep me on the edge. The characters are all fantastic. I can’t wait for the next book.

[Rosie Marie · Rating 4 out of 5]

I know I’m late, but I was sat for this book. The banter. The spice. The plot was everything to me. K.L. Anderson has a way of pulling you into her worlds and making you want to never leave.

The love and pain that I felt between the two main characters was palpable with every scene that I read when they were apart.

Now I want my own demon king.

[Stefanie · Rating 5 out of 5]

If you read ice planet barbarians I think you would love this book! They characters are so adorable together. There is a good amount of spice to plot ratio! I read this book in less then a day it was that good I can't wait to read book 2 and I will definitely be getting a book trophy for this one!

[Confidentlyinthe.clouds Carrie · Rating 4 out of 5]

3.5 rounded

I really felt like if this book was given another few weeks and some tweaks it could be better!

Too many thoughts going at once in chapters making it not bleed together as well

So much promise! i love the plot and the vibes are there. Ended up dnfing at 80ish.

[Shanny Marie · Rating 5 out of 5]

Absolutely amazing I absolutely loved it this book was different to the last due ology the author wrote. This one had Paranormal and supernatural beings in it with fated mate, love, heart break and reunited love. I found it fast paced, gripping and all around fantastic.

[Dian M. Roy · Rating 4 out of 5]

a good read

What an interesting book. This is a paranormal romance that was fun. Secrets and love that is strong and lasting is beautiful and moving. I truly enjoyed this book.

[LadyEllesmere · Rating 5 out of 5]

I received this book as an ARC reader,my review and thoughts are my own though.

(Review coming later)

"For you, ya you⁠— I see you lusting over a demon…same bitch same."

[Ella · Rating 5 out of 5]

Bookstore, Banter, and a Bit of Hellfire

This book is the definition of a cozy read.. well, as cozy as a story involving a demon king can be! Imagine a charming bookstore setting colliding with supernatural mayhem, and you've got the perfect recipe for a binge-worthy escape. The female main character is witty, warm, and refreshingly relatable. Her humor and heart make every page a joy.

If you're stuck in a reading slump, this is your way out. I devoured it in under two days and loved every minute. Seriously, stop reading reviews and grab the book. You won’t regret it.

[Jessica James · Rating 5 out of 5]

That was sooooo cute!!!!! Y'all are going to love this book along with the characters. You have our FMC who moves to a new town as a teenager, mad as all get out the shy book nerd who loves to crochet has to start all over making new friends. That is untill she meets him the boy next door our MMC, she cant believe that this hunk of a boy could like her so what does she do? She puts him in the friend zone four 4 years all the while being secretly in love with her best friend till one night, one exchange of gifts and more, her heart gets shattered.

Years laster she moves back to town and one fateful night she learns that all those inhuman beings she read about in her books are real. When its announced the King of the inhuman will be coming to her town, she doesn't know it yet but her world is about to be turned upside down.

I wont spoil anymore of this amazing book for you, you will just have to go read it for yourself. The quick witty banter, the crazy best friend side characters, and the vivid world this author creates will leave you stunned. Did i mention the spice? Oh my there is a scene where he does naughty stuff to her with his tail!!!! Bravo to K.L. Andersen I love it and look forward to what comes next in this series.