Fantastic Beasts purports to be a reproduction of a textbook owned by Harry Potter and written by magizoologist Newt Scamander, a character in the fictional Harry Potter series. In the series, Magizoology is the study of magical creatures.
Albus Dumbledore, headmaster of Hogwarts, provides the Foreword and explains the purpose of the special edition of this book (the Comic Relief charity). At the end, he tells the reader, "...The amusing creatures described hereafter are fictional and cannot hurt you." He repeats the Hogwarts motto: "Draco dormiens nunquam titillandus", Latin for "Never tickle a sleeping dragon".
Fantastic Beasts and Where to Find Them contains the history of Magizoology and describes 85 magical species found around the world. Scamander says that he collected most of the information found in the book through observations made over years of travel and across five continents. He notes that the first edition was commissioned in 1918 by Mr Augustus Worme of Obscurus Books. However, it was not published until 1927. It is now in its fifty-second edition.
In the Harry Potter universe, the book is a required textbook for first-year Hogwarts students, having been an approved textbook since its first publication. It is not clear why students need it in their first year, as students do not take Care of Magical Creatures until their third year. However, it may be used as an encyclopedia of Dark creatures studied in Defence Against the Dark Arts classes. In his foreword to the book, Albus Dumbledore notes that it serves as an excellent reference for Wizarding households in addition to its use at Hogwarts.
The book features doodles and comments added by Ron Weasley. The comments would appear to have been written around the time of the fourth book, Harry Potter and the Goblet of Fire. These doodles add some extra information for fans of the series (for example the "Acromantula" entry has a comment confirming that Hogwarts is located in Scotland) along with comic relief (such as Ron saying "you're not kidding" when talking about the Hungarian Horntail being the most fearsome dragon of all, a reference to Harry's encounter with one in the fourth book).
Integrated in the design, the cover of the book appears to have been clawed by an unidentified animal.