Not For Disclosure

by Jonathan Caplan

The most serious and sourced book ever published on the subject of UAPs (Unidentified Anomalous Phenomena), previously known as UFOs (Unidentified Flying Objects). Written by one of the UK’s most high-profile and well-respected barristers who has researched the issue for 50 years


For five decades, Jonathan Caplan KC (King’s Counsel) has been pulling together an extraordinary body of evidence about the existence of UAPs, and what he believes to be the world’s greatest ever cover up. Public perception of the UAP issue changed radically in July 2023 when David Grusch – a former Air Force intelligence officer – went public to US Congress under oath on live television that the United States was in possession of crashed non-human craft. His evidence ignited huge interest around the world. Pressure is mounting for the full story to be told, and Not For Disclosure is a landmark book on a subject that the public can no longer ignore.

In his quest for the full story, Caplan has travelled over the years to meet inside sources, including scientists, politicians, intelligence officers and ex special forces, in Washington, Israel and elsewhere. He has collated a vast amount of material from those in official positions who have trusted him and who have been prepared to talk confidentially about the subject. Over the last fifty years he has met and befriended most of the key individuals. His book is a detailed, up to date and in many ways shocking account of this fundamental and disturbing subject. It pulls together the strands of the phenomenon. It raises the debate.

The book includes significant new material including information about JFK and also about secret meetings held by President Truman and Secretary Forrestal. There will also be important and previously unpublished documents from the ‘Majestic 12’ group as well as striking new photos.

Genres: Nonfiction, History

288 pages, Hardcover

Published September 22, 2026

Reviews

[Raakel · Rating 5 out of 5]

No other nonfiction book has blown my mind like this. I have no opinion about UFOs and I am very skeptical of the whole subject but after reading this book I don’t know what to think. The author uses credible sources and provides compelling evidence. This is either the biggest hoax ever or the most life- and universe-altering information ever. I highly recommend this book to any curious person looking to dramatically challenge their worldview, even if they have no special interest in or belief about UFOs.

[paspatel · Rating 2 out of 5]

For a book that purports itself as approaching the topic with the eyes of a sharp lawyer seeking the truth, there is extremely little in this book to support any of the “facts” presented. At the very beginning of the book the author excuses himself for not providing sources for all parts of the book, arguing lots of information was provided on an anonymous basis — that’s fine as it is a reasonable argument, but then the book proceeds with zero citations whatsoever. No footnotes. Very little in terms of document sourcing. Barely anything.

If you can overcome this initial shortcoming, you must be ready to stomach a whole lot of storytelling with very little critical analysis. Most sources are taken as truthful because “why would they lie if they had nothing to gain from it?” or “there’s no reason to believe they’re not sound of mind.” Then the book dabbles into fringe stories, including categorically stating that several sources corroborate the existence of different alien races, including “Nordic-looking” tall ones (a story taken directly from nazi-leaning publications in the US from the 1950s). It is downhill from there.

The only somewhat interesting argument presented are the instances of odd phenomena seen by pilots, and military presence seen in locations where strange things reportedly happened. But this is merely curious and completely inconclusive, especially with the lack of quality in the “analysis” presented in the book.

The main theory presented here is that aliens have increased the frequency of their travels to our reality after the atomic bombs fell over Japan during WWII; since then they’ve been observing us more avidly, either with good or malicious intentions depending on the source you’re consulting. There is a lot of unexplained myth creation in this theory, and throughout the entire book.

Overall, it’s an entertaining read if you read it as speculative fiction or conspiracy literature. Also a must read for fiction authors exploring the alien theme. However, this is not a serious book

[Caleb · Rating 4 out of 5]

Caplan here provides a thoroughly researched and open-eyed summary and assessment of the situation, bringing together the very latest open source intelligence and historical data. He does not shy away the most bizarre facts, instead recounting all that can be credibly sourced, even if it strains our mainstream imagination. The book reads very quickly, and as of 2026 would be the perfect primer for someone interested in seriously engaging with this topic for the first time. After listening to the audiobook, which Caplan compellingly reads himself, I promptly bought it as a Father’s Day gift and hope it generates some good discussion. I especially appreciate the thorough mention of John Keel’s book ‘Operation Trojan Horse’ which I think best explains the true nature of “The Phenomenon”.

I will also add that I grew up as an American non-denominational Protestant Christian and engaging with this topic since 2021 has seriously challenged my faith. In large part thanks to my brother and the book/podcast “Lord of Spirits” I have realized that American Christianity and resulting atheistic scientism have major blind spots when it comes to NHI. I am now quite seriously investigating Eastern Orthodox Christianity, which maintains historical understandings of the unseen and which I think any disciplined investigation of the Phenomenon must contend with.

[M · Rating 4 out of 5]

A book heavily leaning on real life case studies based on individual testimonies and intense, decades long research. It reads well; alternating between descriptive scene setting details about UAPs and analytical comments. Great book if you want to challenge your personal perspective on UAPs and the classified world of alien sightings.

Overall, easy to read and very insightful.

[Del Khan · Rating 2 out of 5]

I purchased this book based on the early overwelming positive ratings. Mistake. This book has nothing new to add to the understanding of this complex phenomenon, and certainly the author is biased at the outset. Disappointed.

[Mike · Rating 2 out of 5]

I do admit to picking up this book off of a used shelf due to watching the movie Disclosure Day. Not because of the theme of aliens among us, but due to a specific scene. One of the stolen files is a video of Nixon showing someone (it is Jackie Gleason) aliens on Homestead AFB in 1973. My family was stationed there in the late 1970's, but there was never any hint that alien bodies were stored there or anything else like Men In Black. So when I saw this book, I checked the index to see if it had references to other Air Force bases we were at. In this case, there were several for Holloman, which is also an intriguing thought. But what I found was a lot of hand waving, blaming aliens for all kinds of things (the Kennedy assassination was due to the threat of sharing alien secrets with the Soviets - ie aliens). Lots of MJ12 docs that "prove" coverups, but nothing substantial that could then be used to show the people of Earth "The World's Best Kept Secret." If it is the most secret thing, why are there a ton of books about such things but no aliens or spacecraft to show?

I found a mention of Holloman with regards to the printing of classified materials. It isn't explained why a USAF master sergeant in the middle of the New Mexico desert had UAP reports and was able to make his own copies to take home. If it was super secret, that wouldn't be possible. For more mundane material, such as that concerning high tech radars on fighter aircraft, all of that would be controlled.

Secretary Forrestal is also mentioned, with his death being due to being tossed out of a window to silence him from blowing the lid on MJ12. While looking into the particulars of his death is warranted, blaming it on alien disclosure is a huge stretch. It links to Kennedy, creating a "men in black" situation where shadow government people are silencing everyone in the know. Except the author who wrote this book. Or others who write extensively on such matters.

Holloman is also mentioned in a CIA doc regarding an "Advanced Contact Group Meeting" in 1953. But what they did isn't mentioned, as there are blacked out spots on the document, which is supposed to be original. A later page states the highly secret group meeting didn't distribute any records to keep people from knowing. But someone knew. It is all very convenient to the narrative that something is supposed to have happened, but there isn't any evidence.

Another mention is of President Eisenhower visiting Holloman AFB on February 20, 1954, to attend a prearranged meeting with representatives of an alien race who flew in with two disc-shaped craft. They have witness statements that disc shaped craft were at the base, but no proof. The author found a statement from Laura Eisenhower that claimed he told her he did have interactions with aliens. Later on in the book there is a mention of another meeting between Eisenhower & aliens in 1955, where he went into one of the saucers for 40 minutes. A bunch of people say they or their dads saw something. If you want to keep such things super secret, doing it at Holloman itself isn't the best idea. Having lived there, the distance from the flight line to the houses isn't all that far & its all flat desert. It would have been better to have done a meet and greet at White Sands, where there isn't much out there, even today.

Then 10 years later, a different set of aliens arrived at Holloman. This time around, its a tall Nordic type, not the grays. These folks met with Air Force & CIA officers. Nothing was written down, but there is supposed to be film taken from a helicopter of the event. But such evidence hasn't been released, though it may not have happened. The Director of the CIA was told he didn't have a need to know, which is such a men-in-black shadow organization trope.

All in all, a bunch of tales strung together to make it sound like there is something going on. But when put up against the experience of living in some of these places and of how lore of a base is passed around, it falls flat. Using a bit of critical thinking, the book doesn't prove anything. The author attempts to use the threat of disclosure to weave a wild thread through various tragic events in USA history. But he isn't afraid of publishing all of the MJ12 documents used & naming names of those who have told him their tales.

[Michelle Parsons · Rating 3.25 out of 5]

This book is at once full of a lot of interesting information and a lot of boring and repetitive information.
Some things the author puts forward sound very convincing and then he focuses on something that seems altogether dubious, like clutching at straws.
However he does at all times admit that much is just speculation, and I understand that what else was he meant to do as there is little hard evidence out there.
I am so fascinated by the concept of alien life, or whatever it is that visits or exists here, that I think I was hoping for more excitement or something conclusive. It feels rather akin to the night I stood on the the very edge of Anglesey and saw in the night sky what I was convinced at the time to be a parade of UAPs, and afterwards stood in Dominos Pizza in Llangefni wanting to grab everyone standing in the queue and tell them what I’d seen… only to later do an internet search and realise that what I had seen was in fact a string of Elon Musk’s Starlink satellites.
I think my disappointment with this book is more of a me problem though. The author wanted to take a comprehensive look at the topic, but I’m more interested in what UAPs are here for and hearing about any messages they have brought, and what they know that we don’t. But ultimately anything we might know about this is purely anecdotal. I have enough self awareness to know that I would have been happy to just be fed more of that, no matter how made-up it was, just because I love ideas and possibilities and speculating.
So the book as it is, is just different to the one I would have loved to read, no matter how unscientific and evidence based it would be.
I think I also might have got along with this book more if I’d read it rather than listened to it. No shade on the author but his reading style is a little underwhelming and monotonous. And there were so many dates and names of people and titles of organisations and projects etc that it was hard to process them all and not feel like it was jumping around in time and place constantly, with me losing track of the year, who saw what, who said what, who admitted or claimed what and who they told, who denied what, who was threatened, who had a motive, who changed their mind etc etc etc.
I just also thought it was worth randomly mentioning that I particularly enjoyed the section about JFK and Marilyn Munroe, despite not really being interested in them previously.
Anyway. There endeth my review.

[Richard West · Rating 5 out of 5]

Once again, I'm sitting here with a book I purchased which Goodreads says won't be published for a few months yet. That's what happens when you purchase a British-authored book from a British bookseller. If Amazon doesn't have it, it hasn't been published! Sigh.

Kind of short at 251 pages this is an up-to-date look at what's going on in our skies, complete with speculation about who is flying these mysterious craft through the world's airspace. As might be expected, there's a short re-hash of older UFO (I still call them that even the correct term these days is UAP) sightings to set the stage for the more recent sightings.

Unlike many people who write these types of books, there's no "they're definitely from wherever" with the author letting the reader make the decision as to what and where these strange craft and the beings which are sometimes seen are and where they come from. This alone, adds a ton of credibility to the information.

If you've read other material on the subject, this might be a repeat of what you've read before, but that obviously can't be helped. If you're someone who is just curious as to what's going on - c'mon we've all seen that Tic Tac video 10,000 times - this is a good primer and introduction to the subject and is worthwhile reading.

I don't know about anyone else, but I'm with Fox Mulder on the old "X-Files" TV series - I want to believe!

[Bullpost · Rating 4 out of 5]

The author presents substantial though mostly circumstantial evidence that there is something to the numerous sightings of UAPs or whatever they are being called on any particular day.
From encounters with "beings" to secret reverse-engineering government projects , theres a lot of aspects to this phenomenon and they are all discussed in the book.
Drawing conclusions as to whats going on gets into trickier waters. The claim that these are physical craft from other planets is hard to get your head around when you know that with our current technology it would take roughly 77,000 years to just reach the first habitable planet from earth.
Also, if as claimed , these craft have crashed on this planet on a regular basis, how come its nearly always the USA who recover and keep these craft ?
Ultimately it will take a leap of faith similar to the commitment of faith millions make worldwide for their religious beliefs for the layman to buy into this .

[William Williford · Rating 2 out of 5]

A condensed, and mostly duplicative historical review of The UAP Phenomenon

It is always hard to provide anything akin to a fact checking of dates, events, names and sigh spelling when it come to reviews of published works about UAP’s. Simply because there is very little factual data available for that purpose. So given that disclaimer; I can only say that this work did not add anything that would serve the purpose of moving the needle on what the UAP phenomenon actually is, what we should expect to happen next, and how we can effectively engage as a human species to answer these two important questions.

[Bill Gibson · Rating 5 out of 5]

Up to date, extremely well researched and detailed as one would expect from a K.C. Has combined all the stories of the past that have had merit and offered proof of source and believability The reference section is a goldmine for those looking for their own authentication of his sources and an eye opener to some of the skeptics. There seems no doubt that the major world govts have known about the phenomena for years but the more I read it , the more I understood the reason for non disclosure

[Martin Sykala · Rating 5 out of 5]

Interesting book. I bought this on the strength that the author is a kc - has more credibility. While he demonstrates that we are definitely not alone, what is scary is perhaps what the uaps are planning? Some are not friendly. America it seems has more information and has only just released more material. Much of it from credible sources.

This book has lead me to purchase other titles from 'respectable' authors. What does the UK, china, Russia know? Only time will tell

[Austin · Rating 4 out of 5]

For the non-human-intelligence-curious among us, this is a very stimulating read! It gets better as it goes — the beginning feels like a hodgepodge of scattered anecdotal stories, but the chapter structure and theses evolve as the book progresses. I zoomed through the second half. The writing style was a bit lacking at times, but overall this is a great read and extremely thought-provoking. The truth is out there!

[John · Rating 4 out of 5]

A good book, not great but at the same time I'd recommend it for a person interested in ufology very lucid intelligent ideas and hypophysis throughout the book, however it felt a little strained and could have been a little diluted down a bit all in all a good book to be read at least once, I did like it, would it be one I'd return to read? I doubt it

[Frank · Rating 2.25 out of 5]

there were a few points that piqued my interest, but from a book that starts by saying he cannot reveal his sources, i ididn't expect much. at the end of the book, i felt the deeper episodes of the 'x-files' were more convincing. As a scientists, I was not convinced. there is hard evidence in it. I was disappointed, but I can still acknowledge the efforts made by the author.

[Sharon Zink · Rating 5 out of 5]

This is a book that I did not want to end. I valued this information because it described the author's qualifications. It was not written for sensationalism. He stated when he described something whether it was likely true or not. A wonderful, understandable, readable book.

[Harrison · Rating 5 out of 5]

Readable, fairly comprehensive for its length, insightful. By far the best general UFO book, especially from a mainstream publisher, on the market today. Caplan did a wonderful job.

[Sean · Rating 3 out of 5]

A lot of interesting facts in his book, but also a bit too many conspiracy theories in the book.

[Adam · Rating 4 out of 5]

I wouldn’t say I am fully convinced but there are a lots of things that are presented in ways that make me question ‘surely not’ and then it appears to be true.
Wild stuff.

[Chris Greensmith · Rating 4 out of 5]

"What is the agenda?"

[E D · Rating 5 out of 5]

intriguing.

Fascinating factual account and very thought provoking. Recommended but go into it with an open mind. Not a sensationalist approach very understated.

[Richard · Rating 0.5 out of 5]

Absolute gibberish.

[Ben G · Rating 4 out of 5]

Bought on Kindle after looking for the 'Dyfed Enigma' that I was hoping too was on Kindle but sadly not.

Recently published and by a KC no less so also hoping that this will really kick the tyres on the 'evidence'. Let's see.

A robust overview of the (mostly) U.S government led projects designed to verify the existence and nature of UAP (unidentified arieal phenomena). I do hope he will follow this book up with another, examining British sightings, especially those in South Wales (e.g. Broadhaven (1970's) and Pentyrch (c.2010)) where the number of witnesses in both cases supports the existence of UAP in my opinion).