I'm proofing the book now, in preparation for submission to Chaosium for approval. This is one well-written book. It's very faithful to the Lovecraft universe and the Mythos which it inspired. The layout is very evocative, as is the artwork. If you are a fan of Call of Cthulhu, you owe it to yourself to check this book out.
There are a number of backgrounds and 3 new roles which are central to the 1920's, which is the primarily setting. However, these can easily be used in other time periods, such as the modern era. Alternately, if you choose to go the Delta Green Route, this book will do that type of game justice. As you might expect, Shadows of Cthulhu provides you with statted Mythos creatures, rules for Sanity and some new mechanics, like Awareness points, which allow you to unlock mythos traits as your characters gain more knowledge about the "things that should not be." If you've never played a Call of Cthulhu game, we got you covered as well, with adventure suggestions, advice on running a Cthulhu game, and even pregenerated Characters you can use "right out of the box." All in all, this is one hot book.
My compliments to the writers and editors. The werecabbages have delivered yet another fine product.