Fiction and fiction.

Genreflecting: A Guide to Popular Reading Interests, by Diana Tixier Herald; edited by Wayne A. Wiegand (6th ed.). (I'm not counting this book against the grand total, because I didn't really read it;) It's more of a reference book: the bulk of each chapter is a list of authors for the genre. Each chapter does have some history on the genre and also discusses any subgenres, listing a few key authors. I could have done with more detail and information, but it was pretty good and gave me a good introduction. Plus I picked it up for free somewhere.

Plum Spooky, by Janet Evanovich. Between the numbers: more or less of the same.