By far the most useful book I've ever read is Prescott Lecky's Self Consistency, a theory of personality. I think it was published in the 40's. It's his theory of the human personality in response to the popular ideas of the time from Freud and various behaviourists. If you want an incredibly useful model for understanding your mind and the various forms of resistance we all have to deal with, I don't think you'll find a better book. (And I've read a lot of them). Last I looked the book was about $150 used, on amazon, but there are PDF's floating about.
