I love Saturday Night Hat by Eugenia Kim! It is full of great ideas for any style hat and contains several patterns. Kim divides the book by the different types of hats and also explains that the hats are meant to be made within an hour or so.
Kim gives ideas for berets, cloches, cocktails, fedoras, caps and sun hats. Kim doesn't forget to include the basics and "vital hat-istics" at the end of the book.