I can only read books that have no significant arc of suspense right before bed. Otherwise I will (a) stay up and finish the book or (b) put the book a way, but be to hyper to sleep.

I also figured, that when I read a book in one sitting in the afternoon or evening I won't be able to sleep very well that night. I will just get to invested and I have a hard time letting go of this feeling evene after finishing the book. So I have to constrict my reading time or read those books during holidays :D