In the Dark Ages, bestiaries were volumes (often illustrated) were written as allegorical or moralizing works on the appearance and traits of real or imaginary animals. They were often thick and lavishly illustrated, and their text described in detail such mythical creatures as griffins, gargoyles, giants, and dog-headed men.
David Day's Guide to Tolkien's World: A Bestiary (also published as A Tolkien Bestiary) is a beautifully written and illustrated bestiary, containing entries on the 129 different races that inhabited Middle-Earth. Fauna and flora, ranging from the Athelas (kingsfoil) plant to the awesome Warg are vividly described, and all of Tolkien's major works (The Hobbit, The Lord of the Rings, and The Silmarillion) are covered. The black and white drawings depict the various races (Elves, Men, Orcs, Istari, Vala, Maia...) and the color plates depict major events from the Creation of the World to the Ringbearers' departure to the West.
A must have for Tolkien fans.