Books? You mean, actual paper books? How quaint!
I think I've only bought one cookbook since we moved aboard, mostly I download recipes from the Web. I use MasterCook software, which lets me search through it's recipe library, plus my personal ones that I've added. For example, I can look for recipes that use an ingredient, like canned tuna that don't require some other ingredient, say, celery - a handy feature when we were trying to make do with whatever had arrived on the mail boat that week!
In paper, though, I have aboard:
2 notebooks of my personal recipes
Lorna Sass: Vegetarian Cooking under Pressure
Moosewood: Lowfat Cooking and Sundays at Moosewood
Nava Atlas: Soups for All Seasons
Jeanne Lemlin: Quick Vegetarian Pleasures
I also keep Anne Vanderhoof's An Embarassment of Mangoes as much for the recipes as the story, and I have 2 no-name Caribbean cookbooks that we picked up in Barbados. I thought McGee's On Food and Cooking was a blast to read, but not really worth the limited shelf space aboard.