Just finished up the latest round this morning when I got to the end of The Book Collector's Guide to L. Frank Baum and Oz by Paul Bienvenue. This is a big fat guide to exactly what the title says, as it describes all of the various major editions of all of the Famous Forty Oz books, lots of other important Oz books, and just about everything L. Frank Baum ever wrote. It's not a full-blown bibliography that describes every point of every edition, but gives enough information and background to figure out exactly what you have. The best part is that all of the illustrations are in color. It is an extremely helpful book (I've already discovered a few things about my own collection I didn't already know). There are a few omissions, notably the 2006 Oz Club reprints of some of their own books, and a few items have come out since this book was published two years ago. But overall this is a great book for anyone who likes the Oz books, particularly older ones, and collectors will find it especially useful.