Happy April Fool's Day!
Did we fool you? Was it funny? Were you really hoping to read more about these fanstastic creatures?
Sadly, such a volume does not exist, as there really are no unicorns or dragons, at least not of the maiden-chomping, fire-breathing kind. However, we think you might be interested in taking a look at a real book that does touch on some of these subjects, Conrad Gesner's Historiae Animalium. In fact, if you look closely, you may find you recognize one of the images contained therein.
From Wikipedia:
Historiae animalium ("Histories of the Animals") published at Zurich in 1551-58 and 1587, is an encyclopedic work of "an inventory of renaissance zoology" by Conrad Gesner, a doctor and professor at the Carolinum, the precursor of the University of Zurich. It is the first modern zoological work that attempts to describe all the animals known, and the first bibliography of natural history writings. The five volumes of natural history of animals consists of more than 4500 pages.
You can view a beautiful version of Historiae animalium online at the National Library of Medicine as well as a related exhibit that links Renaissance science and medicine to the books of Harry Potter.