The main problem I had with this book is that I found it difficult to believe that the murderer isn’t discovered sooner. It is true that the novel takes place in ‘93, so the police had less gadgets than they have now, but they seem to be rather incompetent even when it comes to the most simple tasks, like watching someone. Also, although it is not impossible to believe the plot, lots of things have to go wrong (or right, depending on the point of view) for the killer’s plan to work. There are also some coincidences that can’t be planed but are important parts of the plot. I can’t say much more about this without revealing too many spoilers though.
A good thing is that the different mathematical theories that are mentioned in the book are explained in a way that anybody with high school knowledge of Math can understand them. This is important because while the main characters know the subject very well, most readers will probably need these explanations.