Everyone learns differently so I first ask, can you read a book and retain anything from it? I know that sounds a bit demeaning, but some people can't.
Personally I find a lot of value in a book, I can read and stop to think about what I read at my own pace. I can put something I learned into action and easily refer to it as I am playing. I can also easily go back and reread. Also lots of books contain charts and diagrams that are useful as you play as well.
Another book I like is Harrington On Hold-em Vol 3. It is a workbook that has you play through hands. When I find that I have gone off the rails and am play too loosely, its a good book to think through scenarios and get my head back on the right track.