I thoroughly enjoyed this novel, but not for the reasons I thought I would.
I expected a lot more math. There were some oblique references, but the math was entirely tangential to the plot, no pun intended. I thought that the Pythagorean cult would be described directly, with Pythagoras and his contemporaries as characters, at least in ancient, moldy flashbacks, but he and his mathemagical cronies were long since dead and gone as the story unfolded, and only the splintered factions of his ancient secret society remained. It turns out that this was good enough for a fun story, though, so I'm not complaining.
If there's one thing I love as much as a fun treatment of mathematics, it's impossibly convoluted conspiracy theories, especially if it involves a secret society which clandestinely pulls the puppet strings on the world stage, sending gun-toting thugs after a spunky heroine who threatens their nefarious schemes.
(I hope it will not be viewed as too shamelessly self promoting to provide a link to my own book here, because this illustrates why I like this sort of thing so much: http://www.encpress.com/MM.html )
I'm a firm believer that character is the single most important element of fiction. A riveting plot may keep us turning pages, but it is the characters that stay with us after the last page is turned. I adored the character of Canada Gold. I think I'll remember her long after I forget the difference between the acusmatici and the mathematici. The distinction is already blurring in my mind, but Canada is there to stay.