The Death Ship, by B. Traven is also a great novel. On the plight of poor sailors being exploited by ruthless and greedy ship owners.

The Death and Life of Great American Cities, by Jane Jacobs. A very readable essay on city planning, or the lack of it. A strong argument in favor of diversity, especially mixed neighborhoods - mixed rich and poor, mixed commercial and residential, and so on.

A Pattern Language, by Christopher Alexander, et al. About architecture, but not just architecture, more about the human environment. It convinced me, among other things, that it's better to own a variety of coffee mugs than a matched set.

The Uses of Enchantment, by Bruno Bettelheim. A psychologist on the importance of fairy tales to children, but his insights can be applied to any art form, and any kind of people.

"A great book is one that tells you what you already know, but didn't know how to put into words. Or tells you what you already know, but didn't have enough confidence in yourself to say. Or just tells you that you're not alone." You can quote me on that.