There are lots of books that changed the way I think. An example that may be of special interest to the HN community is "So Good They Can't Ignore You" by Cal Newport (http://calnewport.com/books/so-good/). I have spent lots of time finding the perfect career, until I learned from this book that you must stop finding the perfect career. Just do something that you like enough to spend lots of time on it. Everything else will come. It was very liberating.