Japanese 536/537: Library Guide for Sono Sensei's Class

There is a lot that you can read without buying the books/manga. You should see a very visible link/button for 無料まんが. Sometimes it is at the top of the screen and sometimes it is further down on the menu. You will also see free sections if you browse by category (shonen manga, shojo manga, bungei ...)

BookLive has a link to free materials down the left side. 

BookWalker