I bought this book thinking it was a biography of Riemann. It's not. Riemann shows up for a little bit at the beginning, but the vast majority of this book is not about him. Fair enough, allegedly he kept no diary and made no friends, so there's very little known about him. But the title is exceptionally misleading.
My second concern is "who is the intended audience of this book?" Like, it goes through exceptional trouble to explain natural numbers, but a few chapters later assumes you're capable of following difficult arguments requiring calculus over infinite series. It goes on forever about what a matrix is, but then completely glosses over eigenvalues, despite using them heavily for its later arguments. The final chapter is just one huge derivation of a result that nobody outside of analysis would ever care about.
If you're a math hobbiest, this book is going to be too hard for you. If you have a math undergraduate degree, this book is going to be both too hard for you AND immensely boring at the beginning. The history presented is grantedly interesting. I'd suggest just skipping over the math bits regardless of your skill and skimming through the history. Save yourself some time and frustration.