If you like to read books then one area that you can start as a writer is to publish reviews of books on the bestsellers list. The reason this is a good idea is because it will allow you to drive traffic to your site and make some sells from barnes and nobles or amazon.
People like to read good and bad reviews because it helps them make a buying decision. Its best to be truthful and the best evaluations comes from your own personal experience with the characters and information in the textbooks.
Once you develop your own style you can choose to write several reviews a week, on your blog.