Books: They Ask, You Answer, Inspired, Don't Make Me Think
There is no perfection, only iteration, and the best source of learning is always to talk with users. It also helps to have deep domain experience and insights. Steve Jobs said something about the customerS not seeing leaps in innovation (in UX), so instead look to engineers for these. This is more when you are early in a product and see a large problem that could be solved a very different way than today.
