My greatest obsession (next to books, that is) is gardening. I have partially fed this obsession by ordering some great gardening books for the store (of which I buy half).
The book I love most is Great Garden Companions by Sally Jean Cunningham (ISBN 9780875968476). She details methods of organic companion planting to eliminate use of chemicals. Just pick the types of veggies you want to plant, split them into neighborhoods, add herbs and flowers, and voila, you have a beautiful successful garden. Ok, it took a lot of time initially to plant my garden this way but now that I've been doing it for a couple of years like this, I wouldn't think of doing it any other. It appeals to the planner in me but also to the me that doesn't want to bathe my garden in chemical pesticides. My husband built raised beds for me and it works perfectly with this system.
I use The Vegetable Gardener's Bible by Edward C. Smith (ISBN 9781580172127) in conjunction with Great Garden Companions. While Sally's system is mainly concerned with what vegetables to plant together for maximum benefit, I find Smith's book easier to use for individual vegetable information. He also provides a handy little box listing "good companions" and "bad companions" for each veggie type. I used Sally's book to plan on a large scale and Smith's book to fill in the gaps.
Finally, we just got in a copy of the book Grow Vegetables by Alan Buckingham (ISBN 9780756628901). I discovered it at the library and decided the store had to have a copy (of course one will be going home with me). This is a great reference if you are trying to decide what vegetables you'd like to grow. It is published by Dorling Kindersley (of Visual Dictionary fame) so the photographs are beautiful and the layout very simple to use. It does not contain companion plant information but it has a wealth of information about varieties of vegetables, whether they are early, mid-, or late season harvest, and...did I mention the photographs are beautiful? Certainly falls into the category of what I like to call "garden porn".
Many of us here at the book store are avid gardeners (or aspire to be) so please don't hesitate to ask us for more recommendations! There are also some great cookbooks to go along with the gardening books but that's a blog for another day.