John Harold Saxon Jr. (1923-1996)was an American mathematics educator who authored or co-authored and self-published a series of textbooks, collectively using an incremental teaching style which became known as Saxon math.
This book was great. It was lacking a bit in plot and it was hard to keep track of the main point because there seemed to be a different focus every chapter but I loved how it kept me thinking and it made me learn so many new things.