Cas Russell is really, really good at maths (or math if you're American). She can do calculus in her head fast enough to kill a man, jump through a second floor window, or even dodge bullets. (I know! She's Neo, right?) Basically, she's a superhero whose superpower is maths. Which is pretty cool, actually.
Now, as Douglas Adams and a couple of my more mathematically-inclined friends have pointed out, practically anyone can do calculus in their heads, pretty fast too: that's how you catch a tennis ball. Two times out of three, anyway. But whatever, this is essentially a superhero novel, which means that pointing out that Cas' superpower is unlikely is about as useful as pointing out that a billionaire businessman probably doesn't have time to fly around doing vigilante stuff in a bat suit at night. It's kind of not the point.
So Cas ends up tangling with a mysterious organisation called Pithica, which has typically mysterious objectives and violent tactics to achieve them. It's all rather paranoid. Anyway, she has to try and stop them, because reasons.
Actually, Zero Sum Game is rather good. It has a strong and not necessarily very likable female protagonist, two named POCs, a main character who is disabled, and a psychopath with religion. I enjoyed that everyone here has issues of one kind or another - they're not just straightforwardly "good" - and that the actions they take definitely have consequences; Huang is careful to think about evidence, DNA, fingerprints, etc., in the carnage that our heroes inevitably create, and how they're going to be compromised by that carnage and that evidence. Occasionally the dialogue is a bit wobbly, but it didn't worry me all that much in the light of everything the book does well.
It's well-paced, with plenty of action (and maths), and if there's a bit too much gratuitous killing for my taste, well, that's my problem, not the book's. I probably won't read it again, but it was good fun.