The Venture of Islam vol 1 - Hodgson: Appropriate to historians in the 1970s, he cites nothing and makes plenty of poorly elaborted general claims about civilizational evolution that don't actually matter very much. Still seems foundational enough, and well written enough, to keep reading.
Stream Ecology - Allan et al: Re-reading this textbook from an old class in hopes that it can inform some aspects of natural area management at work.
Tools of the Trade - Sally: Working through some of these very elementary exercises in mathematical-logical thinking is very refreshing.
These lists are meant to be suggestive of the topics I'm interested in. They are not comprehensive.