I really like Margaret Hubert's The Granny Square Book: Timeless Techniques and Fresh Ideas for Crocheting Square By Square for granny squares. I made a baby blanket and all the squares were easily attached to each other, and used another book to make a nice border. The book is spiral bound as well, so it is easy to read as you crochet. I guess there is also a new edition with new things in it... hmmm...
I tend to stick to the basics. I do own this book, however, which has lots of really pretty squares. Be warned that the index is terrible though.