I read a book recently. It was Poincaré's Prize by George G. Szpiro.
The book is the history of the famous Poincaré Conjecture. The conjecture is from a branch of math called topology; a notoriously difficult subject. [Like most people I just can't really think in 4 dimensions; and forget about anything higher] The proof from Hamilton and Perelman ended up using differential equations which was an interesting way to finally get there after nearly a century that the problem had been outstanding. The people who cracked it are first class minds of our generation.
It was a good book. Szpiro took on the daunting task of presenting the history of the conjecture and the eventual proof in an accessible way to the interested layman reader. Szpiro worked hard and was mostly successful but this is a difficult subject to present to a nonexpert audience. It was a good read, challenging but not impossible to get through.
I've often regretted not focusing more on math back in university. I could have, but didn't get a proper math education and I missed standard undergrad courses I should have taken including real analysis, complex analysis, group theory, set theory, probability, game theory, statistics, linear algebra II, applied math, abstract algebra. If I became suddenly wealthy I think one of my top priorities would be to go back to class and take most or all of those courses.