This book is sort of split down the middle. The first half is a very general overview of natural gardening - it's probably an ok starting point if this is a new concept, but that's about it. However, the second half is a pretty solid guide to native plants in the U.S. split by region, and it's pretty useful.
Natural Gardening by Jim Knopf (Time-Life Medical 1996) (640+/-). Here is another organic gardening book with a big dose of natural history thrown in. this volume has much better photos than garden guides. My rating: 7/10, finished 2002.