There are many themes in the book more significant than mathematics. For instance, that Wilson is a Native American and that his allies are Moslem terrorists are both quite significant. However, this website is devoted to mathematics in fiction and so I will focus my attention on a small detail.

At one point, just after he is released from prison, Wilson receives a FedEx package:

Wilson is supposed to have a PhD in engineering. (He is an inventor whose work was considered so dangerous that his ideas were classified by the government, setting up the conflict that is the basis for the plot.) Not all engineers learn advanced mathematics, but I do know of a few whose work in engineering leads them to sufficiently theoretical problems that they could be published in mathematics journals. So, this seems reasonable to me.

In fact, Documenta Mathematica is a real mathematics journal, founded by the German Mathematical Society in 1996 in response to the rising prices of scientific journals. (Its articles are available for free online and the print copies are produced at the lowest possible price.) Although most mathematics journals are produced monthly, it seems that the print version of DM is produced annually, so there would be no "winter issue". Similarly, since there are so many articles in it, the title of Wilson's article would not be on the "title page" but in the table of contents. The title of the article, though meaningless as far as I can tell, has a ring of authentic mathematics to it and does sound like the title of a research article.

One real mathematician (and author) who did research while in prison is Chandler Davis, who included this acknowledgement on a paper he wrote while imprisoned in the United States for his refusal to cooperate with the House Unamerican Activities Committee":

A helpful (anonymous) reader has written in with more information about mathematicians working in prisons.

• Andre Bloch produced all of his mathematical work during a 31 year prison sentence in France.
• Jean-Victor Poncelet (re)invented projective geometry while a Russian POW 1812-14.
• Jean Leray invented sheaf theory and spectral sequences while a German POW (1940-45). Leray was actually a PDEist--he switched to topology so the Germans wouldn't think they could use him.

Note added October 2021: Vijay Fafat has pointed out that André Weil did math research while in prison during World War II and is quoted at MacTutor as having written "My mathematics work is proceeding beyond my wildest hopes, and I am even a bit worried - if it's only in prison that I work so well, will I have to arrange to spend two or three months locked up every year?".