The Rough Guides from Penguin seem to have hit on a winning formula, if the expansion and proliferation of the series is anything to go by. Along with their well-known travel books, Rough Guides now offer a flourishing collection of smart-looking reference books on topics of contemporary interest, from the Templars to Shopping with a Conscience, from Bob Dylan to Climate Change, from Conspiracy Theories to the Velvet Underground.

Their success is slightly puzzling, because it’s not clear quite how you’re meant to use them, or who their target readers are. The user-friendly design of the books invites long-term browsing, rather than reading them cover-to-cover like a novel. On the other hand, they’re not organized alphabetically (at least, this one isn’t), so it’s hard to know were to find a specific subject. Perhaps they’re best seen as the informational equivalent of the Rough Guide travel books, dealing with areas of thought you might already be familiar with, might even have visited a few times, and want to understand in more depth and detail (there’s really nothing “Rough” about these Guides).

The Rough Guide to Unexplained Phenomena is the combined work of two experts in the shadowy zone between the known and the unknown. Bob Rickard is the founder of the Fortean Times, the long-running UK-based “Journal of Anomalous Phenomena” and John Michell is the author of many books on sacred geometry, crop circles, and other mysteries of existence. Their book, published here in a second edition, is thick and handsome, glossy looking, and beautifully designed and produced, full of wonderful photographs and illustrations.

The content is divided into sections on Teleportation, Strange Rains, Wild Talents, the Madness of Crowds, the Fairy Folk, Mysterious Entities, the Haunted Planet, Signs and Portents, Simulacra and Other Images, Monsters, and Living Wonders, along with notes and suggestions for further reading. In other words, the book is jam-packed with hours of fascinating browsing in store for anyone curious about hollow earth theories, blizzards of butterflies, anomalous fossils, man-eating trees, cattle mutilation, spontaneous human combustion, UFOs, poltergeists, crypto-zoological creatures, crop circles, alien abductions, and plenty more.

Unlike many authors who write on these subjects, Rickard and Michell are lively and authoritative writers, engaged and open-minded, neither dogmatic nor overly credulous. Rational explanations for unexplained phenomena are discussed, where relevant, as are the possibilities (and sometimes the proof) of hoaxes. Yet no doors are ever closed completely, always leaving a little room for doubt.

Unexplained phenomena, as Rickard and Michell make clear, are limited neither to time nor place, although certain kinds of manifestations seem to occur in particular places at certain times, as, for example, with the later 19th-century vogue for mediums and spiritualism in Europe and the USA. With the advent and ubiquity of digital photography, one would assume that filmed evidence of such phenomena, if they exist, would be all over YouTube, LiveLeak, and similar sites, but this isn’t the case. Type in “poltergeist” or “levitation” on YouTube, you’ll find a lot of footage, some of it freaky and amazing, some of it suspect and silly, accompanied by lengthy notes from believers and debunkers alike.

In other words, this is an area in which nothing has changed. The founder of the field, Charles Fort, put it best: “Our very existence in this world is an unexplained mystery, and that is something we have to accept and be happy with.”