This slim volume is presented as a facsimile of Harry Potter's own battered copy of the standard Hogwarts textbook — the one on every first-year's supply list — complete with the margin notes he, Ron Weasley and Hermione Granger scrawled across its pages.
Credited to the fictional magizoologist Newt Scamander and first published, in-universe, in 1927, the book catalogues magical creatures in alphabetical order. Each entry gives the beast's Ministry of Magic Classification — from X, harmless, to XXXXX, known wizard killer — along with its habitat and distinguishing traits, running from the familiar Acromantula and Basilisk to the obscure Jobberknoll and Mooncalf.
The real-world edition appeared in March 2001 alongside Quidditch Through the Ages, written by J.K. Rowling under the Scamander pen name in aid of Comic Relief; together the two books have raised many millions for the charity. It works both as a piece of in-universe reference writing and, through the scribbled commentary, as a small extra scene with Harry, Ron and Hermione.