Zero sum game
(Book)

Cas Russell is good at math. Scary good. The vector calculus blazing through her head lets her smash through armed men twice her size and dodge every bullet in a gunfight, and she'll take any job for the right price...until she discovers someone ... intent on becoming the world's puppet master. Cas should run, like she usually does, but for once she's involved. There's only one problem. She doesn't know which of her thoughts are her own anymore.