David Day's A TOLKIEN BESTIARY is a scholarly, definitive and enchantingly beautiful explanation of all the imaginary beasts, monsters, races, nations,deities, fauna and flora of J.R.R- Tolkien's fantasy worlds of Middle-earth and the Undying Lands.
David Day has identified, analyzed and described 129 separate races. Each is lucidly explained in terms of its physical appearance, language, behavior and culture. A TOLKIEN BESTIARY does not retell their stories: its purpose is to make Tolkien’s own books more accessible by identifying his living creatures and explaining their roles in his epic world.
That's one of the reasons I posted the source material as available (free) downloads as well - Day has come under criticism before by Tolkien scholars. I personally found most of his mistakes and liberties in this work to be minor, but I'm not a Tolkien scholar. Nonetheless, the work has a unique artistic touch that regardless of its accuracy, brings the novels to life in a way that surpasses later catalogues, and it was responsible for getting young readers of my generation interested in reading them.
Yeah I realize now that my comment was a tad more aggressive than it was meant to be. I think there's some value in Day's stuff. He gives some interesting perspective and analysis on Tolkien. You just need to remember to take nothing of his as fact.