For fiction books I find that re-reading is like revisiting old friends that I haven't seen for a while. Of course in the case of Non-fiction such as religious texts like the Bible many people say that with each reading they see/understand something that they didn't before or understand it in a new way as the situations in their lives have changed and they are looking for new guidance on how to deal with situation x. So the idea that re-reading something has therapeutic value isn't exactly a new idea. It's been around for quite a long time.
