If you are talking about the books lying around, you know it is optional. Some of them contain clues but they're only for the safes and such.
I open books and notes and immediately close them. I'm too impatient most of the time to read the non-sense and I only open things just in the off chance it affects my score or triggers something. I find the action more satisfying then any other single player game. Only time I need to switch games for more action is when I get the itch for some MP.