Subtitled: "A History and Guide to Role-Playing Games"
Released in 1991, Heroic Worlds makes a heroic attempt to catalog every RPG in print as of that time. He does a very good job overall. He misses some of the smaller independent press releases, and includes at least one item that was never released, but for the most part it's an excellent resource. It's organized by genre.
Schick is close to neutral on many items, but he has his favorites and his dislikes, and lets you know about them. In fact, each chapter opens with his list of what he considers the best in the featured genre.