This my list, ordered by preference, of the books I found valuable. Keep in mind that it's not because a book appear in this list that I necessarily agree with the author. I read everything, and I think in general we should read more books we fundamentally disagree with.
The Denial of Death
In this book Ernest Becker argue that death is the main motivator for human behaviors. I used to agree with him but now I am more of the school of the Universe as a single organism and humans simply being a species trying to survive. In more recent books I read, especially on evolutionary psychology, it became obvious that the human organism is capable of sacrifice (not fearing death) to guarantee the survival of its peers. Like many book, as over the years I change my mind a lot on specific topics, I should read it again to make sure I understant it properly.