It presents data that most survey respondents ascribed their beliefs to reincarnation, feeling that they were other than human in a past life, and that most identified with neopaganism and related new religious movements.

The book sparked scholarly interest in the topic, being widely cited in academic works on otherkin and influencing scholarship of internet-mediated religious movements.

Rather, the concept is rooted in religion, spirituality, or psychology; for instance, otherkin may believe they were other than human in a past life, or in some way possess the soul of a non-human creature.

[4] Though predecessors of the concept predate the internet, the term "otherkin" itself and the communities around it are almost completely internet-based;[5] the phenomenon has been understood as a hyper-real religion, a form of belief that "mix[es] elements from religious traditions with popular culture".

The book opens with a basic introduction to otherkin, defining the term as referring to "a person who believes that, through either a nonphysical or (much more rarely) physical means, s/he is not entirely human".

Based on survey responses, Lupa concludes that otherkin most commonly consider themselves to have been nonhuman in a past life and reincarnated as humans.

The most common subjects of otherkin belief, or "kintypes", in the book's survey sample are therians or therianthropes (real-world animals), vampires, elves or fairies, and mythological creatures such as dragons.

Lupa finds the majority of otherkin in her sample to be neopagans, with common affiliations including Wicca, Heathenry, polytheistic reconstructionism, and eclectic paganism.

As well as new religious movements, she characterizes otherkin as interested in occult magic and the practice of glamourbombing, leaving unusual objects and creative works, such as printed lines of poetry or occult-themed visual art, in public for people to find.

Her interlocutor deemed it non-pathological, suggesting it may be linked to phenomena such as individuation from a conservative family but finding the concept itself compatible with good mental health.

[17] Reviewers received the work positively, praising its research and bibliography,[17][19] its balanced view of the subject matter,[17][19][20] and its voice and writing style.

[21] Nonetheless, elements of A Field Guide to Otherkin received criticism; one reviewer made note of its printing and layout issues, such as poor typographical kerning and difficulty distinguishing chapter and section headings.

[19] Multiple writers discussed how the book handled its unusual subject matter, both praising and criticising Lupa's attitudes towards her survey-takers.

Nico Mara-McKay, editor-in-chief of the occult culture publication Spiral Nature Magazine, appreciated A Field Guide to Otherkin's "rational and balanced view of the subject" but expressed skepticism of Lupa's "fair treatment" of fictionkin, people who believe themselves fictional characters or species.

[17] Michelle Mueller, a minister and scholar at the California Institute of Integral Studies, praised the book but felt that Lupa failed to consider the possibility of non-otherkin readers.