Morgan D. Jones. The Thinker’s Toolkit: 14 Powerful Techniques for Problem Solving:
Nice collection of simple strategies that help thinking and problem-solving; from problem structuring to hypothesis testing, and also some basic trees and matrices to deal with probabilities and decisions.
When I was on jury duty recently, I used his technique for hypothesis testing to list the evidence for and against a “guilty” verdict. It was quite helpful for taking notes and getting all the pieces in order.