Mathematics reading recommendations

Supplemental textbooks

Book	Author	ISBN and purchase links	Why we're recommending it
Introduction to Algebra	Richard Rusczyk	ISBN 978-1-934124-14-7, Amazon paperback	This is a book published by Art of Problem Solving that teaches elements of mathematical thinking as opposed to rote drill. The series has been reviewed very favorably, for example, on Quora.
Measurement	Paul Lockhart	ISBN 10-0674057554, Amazon paperback	Paul Lockhart is a professional mathematician who spent years teaching high school developing innovative curriculum. This offers a mathematical sophisticate's accessible take on geometry and calculus.
The Mathematical Experience	Philip J. Davis, Reuben Hersh	ISBN 978-0395929681, Amazon paperback	The book provides excellent insight into the kind of work that mathematicians do, without requiring the readers to grasp a lot of mathematics.