Some of my favorites...
"Vegetarian Cooking for Everyone" by Deborah Madison
"How to Cook Everything Vegetarian" by Mark Bittman
"A Year in a Vegetarian Kitchen" by Jack Bishop
"The Complete Italian Vegetarian Cookbook" also by Jack Bishop
"Simple Vegetarian Pleasures" by Jeanne Lemlin
"The Modern Vegetarian Kitchen" by Peter Berley
"Fresh Food Fast" also by Peter Berley
"Great Chefs Cook Vegan" by Linda Long
Enjoy!