I found books written by proven pros to have been my best learning tool. But selecting the right one's to read is important. Check this list compiled by aliengenius
I also think some books could be dangerous for your game. I just finished reading Gus Hansen's "Every Hand Revealed" After recording most of his hands in the Aussie tournament which he did win, he put it into print and discusses his thought process. Was very interesting, and his style may be good to use at times. Although his math reasoning was clever, table reads along with allot of luck also came into play often.
Know some people that went to some poker camps with pros, which was costly and same information found in good books. Check that link out. AG pretty clever guy here.