There's this wonderful book by Stephen Covey, The 7 Habits of Highly Effective People. It's sort of the most distilled form of self-improvement literature. When you're in the mood to read it, and ready to hear it, it's filled with brilliant insights.
But I'll admit, it can be a very dry read, if you're not in the mood.
I stumbled across this FANTASTIC video that sums up the habits, in a way that's super accessible. Check it out!