The New Becoming Vegetarian: The Essential Guide To A Healthy Vegetarian Diet
I have been reading the book "Becoming Vegetarian" (see link above) and it is really great. It is not actually a book about how to become vegetarian, but a book about vegetarian nutrition. It talks about why we need vitamin xyz and how to get enough of it, why vegetarians (should) eat tofu, tempeh, nutritional yeast flakes, etc. It also explores common myths about vegetarianism. It is a bit of a dry read since it is so chock full of nutritional details, but I highly recommend it. It is good for new and seasoned vegetarians.
I feel like I might qualify as a nutritionist after reading this book.