I think it's more advantageous to study videotapes, the books are very far behind fast, not that you can not find something that will teach you more for what I read, and I went back, the Ebook, and video lessons are always up to date.
At the Cardschat channel on youtube, there are some cool things about poker.
here in the forum also has a lot of content to improve your game.
I hope to have helped friend. good luck.