I usually use the if I have a question about Middle-earth, and my trusty Tolkien biography by Carpenter for any question about the professor's life.
Does that book just have entries about Tolkien's life, or about everything that he wrote as well? Too bad that there aren't any summaries or reviews on that site.
Still....if I had an extra $175, I might get a copy. Unfortunately, I don't think that will ever happen in my lifetime. heh.