This is one of several reference books I own. The author, Art Bourgeau, owned a great bookstore in Philadelphia, Whodunit? In fact, he may very well still own it. Somebody does. Bourgeau is also an author of several crime novels, including The Elvis Murders, and maybe someone will do a "forgotten books" post on one of them if someone hasn't already.
A few years ago, Duane Swierczynski wrote a nice article about Bourgeau and his bookstore. Here's a link.
But, as usual, I digress. I was going to say something about The Mystery Lover's Companion, which I like quite a bit. It's succinct. In it, Bourgeau rates over 2500 crime novels (that's according to the cover; I haven't counted) from one to five daggers. He also includes a sentence or two about that book and about the author. For a quick reference, you can't beat it. There are four sections: "The American Mystery," "The English Mystery," "The Thriller," and "The Police Procedural."
Copies are available on the Internet for very little. If you like reference books and don't have this one, check it out.