Like the author of this murder mystery, protagonist India Hayes is a librarian at a small midwestern college. Presumably unlike the author, Hayes must prove the innocence of her mathematician brother when he is accused of murdering his exgirlfriend before she marries another man.
There is not much math to discuss here. The brother displays signs of being a typically insensitive and obsessed mathematician on the very first page when he calls his sister at 6AM on the morning of July 4th to ask her to look up YangMills Theory for him.
This one reference is the only mathematical detail. Otherwise, we hear repeatedly how the brother became interested in mathematics in college as a way of getting over his love for the woman who is later to become the murder victim:
(quoted from Maid of Murder)
[He] comforted himself with the blackandwhite world of mathematics and dedicated the same obsessive energy he had in pursuing Olivia to solving story problems I had no way of deciphering.

Despite his apparent effort, he is unable to complete his PhD thesis and so becomes a perennial graduate student. Eventually, we learn that he does not actually like mathematics:
(quoted from Maid of Murder)
That was my first thought, thank God. Because the next day I knew that I wouldn't have to go back to the hole in the basement of Dexler or pound equations into apathetic freshman heads or create some useless theorem so I could publish my dissertation.

So, though this book may be fine as a mystery, the author really has no particular appreciation for mathematics and nothing to say about it beyond making use of the negative stereotypes of the field and its practitioners. 