Mark Bittman is looking for the best cookbooks and you can give your two cents. I have an entire bookshelf of just cookbooks yet I don't use many often so I had to think about this pretty hard. I don't know why I've collected so many cookbooks but here are the few I do use:

The Ultimate Diabetes Cookbook by Carol Gelles - I'm not diabetic. It's just that it's a reliable source for healthy good stuff and when I'm feeling uninspired, I know I can get a good fool proof recipe to serve to guests.

The Cake Bible by Rose Levy Beranbaum (see I'm not diabetic) is a great go to for cakes.

Vegetables by James Peterson is a good reference.