Morris Kline while doing some Engines related research. His book, Mathematical Thought from Ancient to Modern Times, was quite a page turner. At over twelve-hundred pages I admit I have yet to finish it. In fact, I probably won't. But what makes the book so fascinating is that it focuses on how we've thought about mathematics over the centuries, not mathematics per se.
Morris KlineKline was an avid student of mathematical history and wrote many historically oriented books. Mathematics in Western Culture. Mathematics: A Cultural Approach. But he's perhaps best known for his work related to the teaching of math.