One of my favourite non fiction authors is MIT Professor of Psychology Steven Pinker. He writes withe rigour (and plentiful footnotes!) of an academic press but is effortlessly readable cover to cover.
I picked him up part way through his career writing bestselling psychology books for the public with The Stuff of Thought - Language as a Window Into Human Nature. Understanding how people think is central to my work as a magician and this book was extremely insightful for me. I've since taken to picking up everything he writes as it comes out.
A later important follow-up was The Better Angels of Our Nature - Why Violence Has Declined. The central argument of this book is that everyone whining about how things are going downhill in society and the world is going to Hell in a handbasket is, quite simply, wrong. Oh.... and here's 700 pages of the evidence why they're wrong. Which would seem to qualify this as one of the most important non-fiction books ever written.
He recently gave the talk below, which seems to be a bridge between his last book, Angels, and his forthcoming book, Enlightenment Now, which seems to be about how the values of the enlightenment are the best way forward if we want to continue the trends highlighted before.
American readers are encouraged to watch through to the very end.