Probably known to most people, but "Guns, Germs, and Steel" by Jared Diamond turned me on to a lot of things. The work covers many topics, including history, geography, evolution, giving a very wide view, which serves as a good starting point to start exploring some of these topics deeper.
Ages ago, "Gödel, Escher, and Bach" turned me from a kid who liked computers into someone very into music, math, philosophy, and literature. It does a great job of showing the reader the joy of playing with abstract concepts across several fields, including writing.
The Wild Trees by Richard Preston about climbing Giant Redwood trees in California. It started my own tree climbing which I learnt entirely from YouTube and some falls. In the book the author describes making love in a hammock high in the trees. Hell, what could be better than that?