billswift

How to Solve It seems to be aimed at math teachers, but it is useful for almost anyone wanting to learn more math

as well as The Goal

Sowell's Basic Economics is the easiest to read one I have seen, and for the math phobic it has no equations.

I will definitely second Atul Gawande's Checklist Manifesto.

I read that 2 years ago, and I agree it is excellent.

Also Thomas Sowell's Knowledge and Decisions covers roughly the same ground as Hayek's Use of Knowledge in Society, but is newer and more readable.

Eric Temple Bell's "Mathematics: Queen and Servant of Science" is a bit dated but an excellent history of math for someone interested in learning to do advanced math

Davis and Hersch's "The Mathematical Experience" is a fairly easy read about philosophy of math, how it is used, and a bit about studying math.

one of the best books on improving your thinking in general that I have ever read

The best Precalculus textbook I have used is Swokowski's "Algebra and Trigonometry with Analytic Geometry" which is clear, concise, and has lots of problems.

Another really good, if idiosyncratic, book is David Friedman's Hidden Order: The Economics of Everyday Life.

P J O'Rourke On the Wealth of Nations does an entertaining and fairly accurate job of "condensing" it.