The simple act of reading any book doesn't make you a better person. However the subsequent incorporation of the ideas held in the book to your own life may well have an effect (just ask any Christian about the bible, a devout muslim about the Koran, any 16 year old who has just read Atlas Shrugged, Myra Hindley about the Marquis de Sade). Whether the changes result in a human who is better or not may end up being a subjective judgement, but you can definitely say the human is acting differently as a result of those ideas. They may act differently such that you appraise them as a 'better person' or a 'worse person'. Without the means of transferring ideas and knowledge to the next generation through books, I think it's fair to say that the human race would have advanced much slower. In fact picking up the right book can inform us about the effect the Gutenberg press had on our culture.