My battery life has been better lately. Maybe I was just using it a lot when I first got it and I should take that into account. I use mine daily now (mainly for playing games and reading and some web surfing) and by the end of the day I do a full charge overnight. If I use it a ton I'll have to charge it at some point earlier if I want to use it that night. Then other days I have not charged it at all, depending, and I go 2 days on a charge.
Bad Ass Battery app says I'm getting 8 hours 20 minutes from my battery. Take that how you will, I don't know how accurate it is really.
I never did remove those pdf's and non Amazon books so I don't really think they take from the battery any more than the Amazon books do.