In Revelations there are bookstores sprinkled around the map. You can buy treasure maps at bookstores - very useful. You can also buy books at bookstores - less useful, I think. Is there any reason to collect books (other than the simple pursuit of 100%)?
They are kind of like the paintings from Assassin's Creed II and Brotherhood: there is no real in-game point to them beyond filling up a room at the hideout. You can't read them or interact with them in any way other than getting some information about the book and its author.
You do get an achievement for buying all the books from every city and doing the Niccolo Polo book missions, but that's about it.