Greg Egan is a science-fiction writer that holds a B.S. in Mathematics (and has co-authored a paper with John Baez). He often manages to insert some advanced maths, physics and computer science content in his novels(: for instance, listing only mathematics, fiber bundles in Diaspora, Einstein's equation for general relativity in Incandescence, Cantor sets and commutative diagrams hypercubes in two the short stories whose title The Infinite Assassin and Glory.
His story Dark Integers deserves special mention; it is a sequel to Luminous, best read in order.
It is truly science fiction written for scientists and mathematicians in particular; they are the only readers that are able to grasp fully both the casual references to advanced mathematical content and the grand ideas underlying his stories. Even after a master in pure maths and a phd in numerical analysis, often I have forgotten)feel that I do not know enough geometry and theoretical physics to get all the facets and implications of what he writes.
This feature sets him apart from most other writers in this list, who address maths from a popular-science point of view.
On the top of my head, I find it difficult to name a novel of his that does not feature a scientist among the protagonists.
ADDED by AK: His story "Dark Integers" deserves special mention (ADDED by DR: and is a sequel to "Luminous", best read in order).