In this sequel to One Word Kill, math prodigy Nick Hayes develops the theory of time travel that his future self used to go back in time to meet himself in the first book. The idea, which sounds neat even if it doesn't entirely make sense, involves making a "splash" in spacetime so that a small piece breaks off like a droplet tossed up from the surface of a lake after a rock has been tossed in.
Nick also meets his daughter from a different future. (Again, this is not much of a spoiler. It is revealed to the reader well before the end of the book, and a thoughtful reader  especially one who knows who Lady Gaga and the Red Hot Chili Peppers are  will have figured it out even before that.) His daughter is also a mathematician, an even better mathematician than Nick himself. ("If I was going to be upstaged mathematically, then having the person to do it be my daughter was the best option. That still didn't mean I had to like it, though.") She has worked out the mathematical theory of how the universe reacts to paradoxes caused by time travel. (In nonmathematical terms: the universe hates them and tries to eliminate them by killing the people who caused them.)
There is quite a bit more discussion of math in this book than in One Word Kill. Here are my remarks on some of it:

Nick's father was a famous mathematician who committed suicide when Nick was still young. Although the first book suggested that his father's cancer was the reason he took his own life, this book suggests instead that it was because he discovered a flaw in his own published math research. Nick claims to have fixed the proofs.
 Nick attends a crowded math research lecture by Professor Halligan, with whom he later collaborates. He comments on the fact that everyone in the audience "apart from one severelooking woman" was male. The book takes place during the 1980s, and he also says that the ratio of women to men in math "improved each year as the sexism leaked out of the system."
 There's some nice metamathematical philosophy as Nick talks about how he feels about math:
(quoted from Limited Wish)
Mathematics is its own language. The language of everything. It doesn't need someone to explain it. I explains itself and leaves almost no room for ambiguity.
I was always good at maths but it wasn't until I started to take the stuff seriously that I began to see the beauty of it. A good mathematical proof is a gem. I sparkles in the same way, and like a diamond it's impervious to time. It takes and multiplies the light of understanding, refracting it through many facets.

 During the lecture, Nick notices a mistake and (without thinking) says so out loud. The lecture halts and the room goes silent as he (a teenager who looks unwell as he is receiving chemo treatment for his leukemia) and the most famous mathematician in the world discuss math that nobody else understands. Nick ends up at the board writing over the professor's equations. The professor realizes that he's in the presence of a genius, one he desperately wants to collaborate with.
 Unfortunately, even though his biography claims he worked for 20 years as a "research scientist", I don't think Lawrence is particularly good at writing mathematical dialogue. Although he's using mathematical terms, they never seem like the right terms for what they are discussing. For example, when Nick is trying to understand his daughter's work on paradoxes he says:
(quoted from Limited Wish)
"And those look like terms you find in work on turbulence." I frowned. "And that looks suspiciously like the generator for the Mandlebrot [sic] set..."

And, when he supposedly finds a mistake in Halligan's work Lawrence writes:
(quoted from Limited Wish)
"Those paths are homotopic in C. In equation 86. The existence of the first homotopy follows from the continuity of the ffunctions," I said.
...
He returned to the equation in question and jabbed at it fiercely with his marker pen. "Nonsense. The homotopy follows from the compactness established in ..."

So, it seems that they agree that the curves are homotopic but disagree about how they know that they are. That's not much of a problem, is it?
 Towards the end it says:
(quoted from Limited Wish)
I wasn't yet seventeen, but I knew enough now to understand that the world was more complicated than mathematics, however advanced, and that there were no perfect solutions to it.

I found it very strange how similar the plot of this second book in the series was to the first. There are some differences: he meets his future self and his future/alternate universe daughter rather than just his future self, and they break into a nuclear power plant instead of a facility producing microchips, but the plot and story arcs of the two books were remarkably similar. In fact, Nick even comments on this at one point himself. His daughter suggests that it might be because of some sort of temporal "resonance", or could just be a coincidence. And maybe the author intended the similarities to be deep. However, I must admit that it seemed like lazy writing, as if the author only had one idea for a book and was using it twice. Aside from that, however, I actually preferred Limited Wish to One Word Kill, and not only because there was more math in it! Even though this is the book in the trilogy with the most mathematical content, it is also worth checking out the sequel Dispel Illusion where the whole time loop that has been set up in the first two books is fully developed. 