Limiting myself to books not yet mentioned:

Einstein's Dreams by Alan Lightman is notable for the very high - mesmerizing - quality of its prose. It does pertain nominally to physics, not pure math, but only (at the time) of the most theoretical kind, far closer to math than most physics of the day.

As to the Foundation series, which has been mentioned here before since Hari Seldon is a mathematician, it is worth noting that in the later novels of the first trilogy key roles are played by a community of mathematicians whose mathematical research is critical to the advancement of the plot.

The French Mathematician by Tom Petsinis is a fictionalized account of Galois; I enjoyed it.

Also, Engima by Robert Harris is loosely based on Turing's work in the war. It is not entirely without points of interest. Harris is a pretty good writer, although the story is perhaps not his best.

Limiting myself to books not yet mentioned:

Einstein's Dreams by Alan Lightman is notable for luminous prose. It does pertain nominally to physics, not pure math, but only (at the time) of the most theoretical kind, far closer to math than most physics of the day.

As to the Foundation series, which has been mentioned here before since Hari Seldon is a mathematician, it is worth noting that in the later novels of the first trilogy key roles are played by a community of mathematicians whose mathematical research is critical to the advancement of the plot.

The French Mathematician by Tom Petsinis is a fictionalized account of Galois; I enjoyed it.

Also, Engima by Robert Harris is loosely based on Turing's work in the war. It is not entirely without points of interest. Harris is a pretty good writer, although the story is perhaps not his best.