1. UFOs: Generals, Pilots, and Government Officials Go on the Record, by Leslie Kean View this photo on Instagram instagram.com Leslie Kean's 2008 book is notable both for her prior experience as an esteemed investigative journalist and the breadth of strange and compelling UFO cases it explores. The book includes strange and chilling firsthand accounts from a retired Air Force major, an Air Force colonel, and a retired chief of the FAA’s Accidents and Investigations Division — in addition to several other distinguished sources. Kean's book is well-written, spooky, and completely un-put-downable. 2. The Mothman Prophecies, by John A. Keel View this photo on Instagram instagram.com For a little over a year, starting in 1966, the town of Point Pleasant, West Virginia, was besieged by a series of inexplicable sightings — all of a bizarre, giant, winged figure which came to be called "The Mothman." In this bestseller, journalist John A. Keel explores these and other, seemingly related strange events. 3. Witness to Roswell: Unmasking the Government's Biggest Cover-Up, by Thomas J. Carey, Donald R. Schmitt, and Edgar Mitchell View this photo on Instagram instagram.com In this book, which highlights the infamous 1947 Roswell Incident — in which some believe a UFO crash landed in Roswell, New Mexico — the authors delve deeply into news reports, historical data, and witness accounts to explore what really happened. The detail presented is almost overwhelming, and many readers will be hard-pressed to deny that something beyond a mere weather balloon was found that day. 4. Communion, by Whitley Strieber View this photo on Instagram instagram.com Whitley Strieber's 1987 account of his and his wife's repeated experiences with alien abduction — and their subsequent interviews with counselors and hypnotists — has drawn enduring, international interest and acclaim for its careful open-mindedness, the stirring writing style, and the vivid, convincing detail in which Strieber relays his story. 5. Encounter in Rendlesham Forest, by Nick Pope amazon.com Though perhaps less famous than the Roswell Incident, the Rendlesham Forest Incident — which took place in Rendlesham Forest, England — is considered the best-documented UFO incident in world history. (Notable among the evidence — abnormally heightened radiation readings from the trees said to be in the direct line of the crashed aircraft.) In this book, former British government UFO investigator Nick Pope incorporates witnesses' shocking first-hand stories and a number of formerly classified documents on the case. 6. The Interrupted Journey, by John G. Fuller amazon.com First published in 1966, this bestseller tells the tale of the Betty and Barney Hill abduction, alleged to have taken place in New Hampshire in 1961. The couple was driving home late at night when, they said, they spotted a craft. Two hours later, they arrived in Portsmouth with no recollection of the time that had passed. For many months afterward, both Betty and Barney underwent hypnosis and psychiatric evaluation, and more and more details about the incident began to emerge. This book presents the complete account. 7. Mirror Earth, Michael D. Lemonick amazon.com This book comprises a more, ah, down-to-Earth discussion of outer space and its possible inhabitants, examining astronomers' and a group of competitive "exoplaneteers'" search for another Earth-like planet — and with it, alien life. 8. The Day After Roswell, by Philip Corso amazon.com In this tremendously popular look at the Roswell Incident by Colonel Philip J. Corso — former member of President Eisenhower’s National Security Council and former head of the Foreign Technology Desk in the US Army — the author claims to have personally managed several recovery projects of alien artifacts found in the crash, later converting alien technologies for American use. 9. Chariots of the Gods: Unsolved Mysteries of the Past, by Erich von Däniken View this photo on Instagram instagram.com A classic for anyone who's ever watched Ancient Aliens, this book examines the popular theory that alien beings first visited Earth a long, long time ago — and that the evidence is visible in the pyramids, ancient ruins, and our very own human race (whom the author claims are descendants of these alien beings). 10. The Invisible College: What a Group of Scientists Has Discovered about UFO Influence on the Human Race, by Jacques Vallee amazon.com Jacques Vallee, French researcher and PhD in computer science, has long studied aerial phenomena, and in this book examines possible links between patterns in UFO sightings and human behavior and events — and how much of it takes place in the realm of the human psyche. 11. Area 51: An Uncensored History of America's Top Secret Military Base, by Annie Jacobsen View this photo on Instagram instagram.com This national bestseller explores the storied covert history of Nevada's Area 51 (home base to many an extraterrestrial conspiracy theory), and includes exclusive access to 19 eyewitnesses (now between the ages of 75-92) who worked in secret on the base for many years. 12. The 12th Planet, by Zecharia Sitchin amazon.com No UFO enthusiast's library is complete without at least one book by Zecharia Sitchin, perhaps the most famous proponent and writer on the ancient astronaut theory, which states that the ancient Sumerians were created by an alien race called the Annunaki, who hail from the planet Nibiru. This book, first released in 1976, is now in its 45th printing.