I rely on Joy of Cooking for lots of basics- got mine as a gift over 25 years ago!

A source of a lot of interesting recipes from all over the world- Jewish Holiday Cooking. It's over 20 years old and I don't know how easy it is to find, but I everything I've tried from it was great, and there are quite a few vegetarian options (mostly w/ dairy products).

Another cookbook that might be completely out of print, that I got a really long time ago - The Vegetarian Epicure. Though my copy is falling apart, I still get great reviews on the Cauliflower Curry recipes, and I wowed a college dinner party with Asparagus Pastry.