The Organic Gardener's Home Reference: A Plant-By-Plant Guide to Growing Fresh, Healthy Food
This is truly a one-stop comprehensive guide to organic gardening: it is a big book filled with techniques, definitions, solutions to gardening problems, and a huge listing of organic gardening resources.  It's one of the most thorough guides I have seen for organic gardeners--it is well indexed and annotated, and covers all climate zones and growing conditions. If this book doesn't get your motor running about the garden, well, maybe you'll want to try a different hobby. I think it should be a part of any true gardener's library, covered with notes, muddy fingerprints, and with the well-worn pages.