"Light and Color in the Outdoors" by Marcel Minnaert. The book goes into the physics of a lot of outdoor phenomena; you will be amazed at the things you never noticed or thought about before reading it. "The History and Social Influence of the Potato" is a pretty good time. "Politics of Qat: The Role of a Drug in Ruling Yemen" may sound way too niche, but it's fascinating as a study of transportation in a drug economy. Qat is a perishable leaf (like salad) and the politics of the entire region depend on who can more reliably deliver it to gunmen.
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