Root of Unity by S.L. Huang. ★★★1/2
Cas Russell and her mathematical superpowers are back! Root of Unity is the third book in Russell’s Attic series (start with Zero Sum Game), a series of fast paced, science fiction action thriller’s. Cas Russell has superhuman math abilities which she uses to work as a mercenary, instantly calculating the trajectory of bullets and the exact parabolic arcs needed to leap between buildings.
However, Cas is also trying to become a better person. It’s a strange journey for our anti-heroine, and Roots of Unity opens with her “falling off the wagon” – killing people again after she’d gone all of book two without murdering anyone. Over the course of the last two books, she’s found something very new for her: friends. Cas is horrible at interpersonal relationships, but she’s trying her best to learn this friendship thing.
So when one of her new friends, Arthur, who acts as her moral conscious of a sorts, needs help, she decides to help him out, even if she’s not getting paid. Arthur’s childhood best friend is a mathematician who’s developed a world shaking proof that could undo the encryptions that the entire digital world depends on. And it’s been stolen.
Meanwhile, questions about Cas’s past are piling up. I’ve always wanted to know more about Cas’s background. How did she get her powers? Where did she come from? While Root of Unity doesn’t provide answers, the questions are starting to gain a greater urgency as Cas’s dreams worsen and she realizes the limitations of her own mathematical powers.
Roots of Unity was the exact book I needed at the moment I read it. Something fun and fast paced with characters I could care about. Cas is such a complete mess, which is probably why I loved her character so much. Immediately after finishing Roots of Unity, I headed straight to book four so expect to see a review of that before too long!