I recently thought of something else related to why one would prefer a "new" book to an old one. There's a certain suspense involved in reading a work in progress. Waiting for the next installment, making guesses at what's going to happen next, discussing your theories with your friends who are all at the same place in the story as you are, and so on, are all things that rarely, if ever, happen with old stories as intensely as they do with new stories. A message board I used to frequent had an extremely long-running discussion of Stephen King's "The Dark Tower" series that died shortly after the final book was published.

In other words, with new stories, you can give someone something to anticipate. Old stories tend to be well-known to the point where everybody already knows what happens, and the anticipation only lasts as long as it takes you to get from the beginning to the end.