My favourite is the Moosewood cookbook which is available from Amazon. It has really tasty recipes, but also encourages you to experiment with your cooking
My only word of warning was the book was originally published in the 1980's and a lot of the recipes use larger quantities of cream and cheese than you might consider to be healthy.
I believe there is a new edition which cuts down on these, but I just reduce the amounts or substitute yoghurt from cream.