One way of commersializing your blog is signing up to Amazon affiliate-program.
You can have a virtual bookstore on your website by linking to pages at Amazon. If links from your site result in sales, you get a commission (4% to 8,5%). When a link from a site is part of this program, there will be an identifier at the end of the URL so Amazon knows who to credit for the referral. Participants are supposed to clearly indicate that they are affiliated with Amazon.