Whenever I need a mental reset back to the basics, I reach for The Manual. It's a translated collection of Epictetus' fundamental teachings, and perhaps the most useful 60-quick pages I've found anywhere. And 60 pages is being generous — many pages are just a few pithy sentences and then emptiness. It's hard to imagine slamming directly into such accessible wisdom and insight in less than an hour's read, but this is that book.