Otherkin is a subculture, or rather a cluster of several subcultures, dominated by people who claim to be animals. There are also Otherkin who identify as vampires, elves, angels or characters from fiction. There is almost no material on Otherkin on Amazon (unless you count novels about shape shifters and some outright pornography), probably because most members of this subculture are very young and communicate mostly through the web, rather than through books. Lupa's “A Field Guide to Otherkin” seems to be the only exception to the rule. I already reviewed it once, but since it has more than one product page…here we go again!
First, some objections: the book is grossly overpriced, the print is too small, and the italicized sections almost impossible to read (at least if you're a near-sighted non-kin).However, since no other printed work on Otherkin seems to exist, you will probably have to “bite the bullet” and procure this volume anyhow.
On the web (that would include Youtube), I get the impression that most Otherkin, at least today (mid-2010's) are teenagers (often around 15 or 16 years of age) experimenting with their identity. This would explain why many Otherkin also claim to be Queer, Demi-sexual, “Self-diagnosed Autists” and the like. These purely experimental Otherkin are hardly even mentioned in Lupa's book, published in 2007, focuses more on Otherkin with a “spiritual” orientation, usually rooted in Neo-Paganism or New Age. The Otherkin concept is related to ideas popular in such circles: reincarnation, shamanism, totem animals, walk-ins and channeling. There is also a connection to fantasy literature. Of course, the most obvious parallel to an older belief is that of shape shifting. Otherkin who identify as animals call themselves “therianthropes”, compare lycanthrope (werewolf). Lupa herself has written another book about shamanism and ritual magic, and is therefore Neo-Pagan in orientation (at least broadly speaking – terms such as “pagan” and “heathen” are apparently contentious, but that's another book!)
There are also obvious similarities between the Neo-Pagan Otherkin described by Lupa and the experimental Otherkin roaming the wilder parts of the web presently. For instance, there is a strong overall tendency to identify as “cool” and dangerous animals. Wolves, big cats, werewolves and dragons are grossly overrepresented, which is surely a problem for those who believe in literal reincarnation. Why don't uncool animals, such as rodents, insectivores or slugs, reincarnate as human teenagers, I wonder? Apparently, it's always been common in this subculture for the participants to accuse each other of being fake! There is also a slightly sinister subset of Otherkin: those who self-identify as vampires, either “psychic” or “sanguinary”. Here, there seems to be an overlap with the Goth subculture.
Apart from “A Field Guide to Otherkin”, those interested in this peculiar phenomenon might want to read Doreen Virtue's “Earth Angel Realms”, a book also recommended by Lupa. It's not a book I particularly like (I review it elsewhere on this site), but if the idea of shape shifting or “being born in the wrong body” appeals to you (or simply appalls you) you might find it somewhat useful. Finally, there is the idea of Starseed, also known as Star People or Lightworkers, which is a New Age UFO belief about aliens from other planets being reborn on Earth to aid in Earth's evolution. Lupa says very little about this, but the similarities are obvious.
I admit that I don't believe any of it (I've never seen an Otherkin claiming to be a reincarnated chimpanzee or Neanderthal, the most logical alternatives if you believe in evolution!), but I will nevertheless give this book four stars.