Reddit mentions of Unexplained!: Strange Sightings, Incredible Occurrences, and Puzzling Physical Phenomena

Hello, Brother!

Okay, so if it's non-fiction you want, then I know just what you need.

If you want a good overview, Mysterious America by Loren Coleman, who's more or less the godfather of cryptozoology, is a superb first entry for anybody interested in cryptozoology. I especially liked the sections on "Panthera Atrox." There are sections on phantom ships and other more mystical elements of the Fortean, and some might find its focus on North America a bit limited, but I'd still recommend it.

Mysterious America: The Ultimate Guide to the Nation's Weirdest Wonders, Strangest Spots, and Creepiest Creatures

I'd also recommend Coleman's "field guides." These don't go into quite as much detail as Mysterious America, but they do provide a rather intriguing look at the diversity in sightings of animals that do not belong. The Field Guide to Bigfoot and Other Mystery Primates and The Field Guide to Lake Monsters, Sea Serpents and Other Mystery Denizens of the Deep are useful, as is the similar, if somewhat dated, Cryptozoology A To Z: The Encyclopedia of Loch Monsters, Sasquatch, Chupacabras, and Other Authentic Mysteries of Nature.

The Field Guide to Bigfoot and Other Mystery Primates

The Field Guide to Lake Monsters, Sea Serpents and Other Mystery Denizens of the Deep

Cryptozoology A To Z: The Encyclopedia of Loch Monsters, Sasquatch, Chupacabras, and Other Authentic Mysteries of Nature

Coleman's written some other books as well, focused on individual cryptids. Bigfoot: The True Story of Apes in America and Mothman and Other Curious Encounters are among the most notable.

Bigfoot: The True Story of Apes in America

Mothman and Other Curious Encounters

Moving on, I found another book that functions as a good overview of cryptozoology is Jerome Clark's Unexplained!: Strange Sightings, Incredible Occurrences, and Puzzling Physical Phenomena. Clark gets into a bit more Fortean elements than Coleman does, but his book also includes some cryptids that Coleman rarely pays attention to--including living dinosaurs.

Unexplained!: Strange Sightings, Incredible Occurrences, and Puzzling Physical Phenomena

If you have a particular taste for feline cryptids--surviving Panthera Artox, surviving saber-toothed cats, whatever the heck the ones is--then I must recommend the writings of Karl Shuker. Shuker is a prolific writer, and to list his books would take up a lot more space, but if I had to choose one, I'd recommend Extraordinary Animals.

Extraordinary Animals: Revisited

You didn't mention whether you were an American, but Stackpole Books has a "Monsters Of" series that has the folklore of individual states in the United States.

Following up on that, if you live in California, or if you have a fondness for sea monsters, then you may also like the book Mysterious Sea Monsters of California's Central Coast.

Mysterious Sea Monsters of California's Central Coast

Now, I know you said you weren't looking for novels, but if you have kids of your own, or you have younger relatives who might like the material, there's always the works of Roland Smith. Sasquatch and the "Cryptid Quartet" which includes Cryptid Hunters, Tentacles, Chupacabra, and Mutation are all great reads for middle readers, or for the young at heart.

Sasquatch

Cryptid Hunters

Tentacles

Chupacabra

Mutation

You'd probably like Unexplained! Strange Sightings, Incredible Occurrences, and Puzzling Physical Phenomena...I read it years ago and enjoyed it.