The Compass of Pleasure by David J. Linden. It's about the "pleasure circuit" in the brain: the anatomy and physiology of brain cells that result in our experiencing pleasure.
If that sounds a geeky, it's absolutely not. Linden's book is a delight (his occasional efforts to teach the reader a little brain science not withstanding), unfolding like a mystery in easy prose with touches of humor. First, he shows us that there is, in fact, a particular area deep in the brain that is responsible for pleasurable feelings, and when it is possible to stimulate it directly (as in animal experiments and one unfortunate and unethical human one), the individual would stimulate it until they die, it is so compelling.
Linden then explores how the pleasure circuit is involved in addiction, love and sex, memory and learning, each chapter adding clues to the puzzle of pleasure. He looks to evolution for the reasons we each (and just about every other organism on earth) have one. His observations are both refreshing (pleasure is just as important with virtue as vice) and disturbing (his view of the future of pleasure would make on scary sci-fi novel).
I was a psych major in college (I'm not saying how long ago), so have a good basic understanding of neurons, neurotransmitters, and the like. I therefore did not spend the time to read all the extra detail on neurobiology put in the book. I think Linden could have left it out completely, but with my basic understanding of the brain already at hand, I'm a not a good judge of how a novice would fair. And Linden is a good professor and thinks his readers will benefit from understanding some of how the brain works under the hood, bless him.
Still not sure if this book is for you? Hear what the author himself has to say when he was a guest on NPR's Fresh Air in June 2011 talking about the book.