As a vegetarian, Thanksgiving is fraught with peril. I don't want to be that girl who wanders around poking at everything, asking "Is there lard in this?", so it's easier if I just handle a lot of the cooking myself. And here are the cookbooks that will help me:
The fine people at Cook's Magazine want their recipes obeyed. They've already spent countless OCD-fueled hours making sure every direction is exactly right, so all you need to do is follow their directions to the letter. Some cooks might find this irritating, but I think it's downright soothing. Thanksgiving is a time for pie, not culinary creativity.
Deborah Madison's cookbooks are slightly less anal, but not much. Her recipes are extremely labor-intensive, but the final results are always delicious, and sure to be appreciated by vegetarians and meat-eaters alike.
I live in the Pacific Northwest, so Greg Atkinson's collection of recipes based on local ingredients is a wonderful resource. I encourage everyone to find a good local cookbook, one that forces you to explore the best food your region has to offer.