Significantly better than the first book in some ways. While the macro/micro levels are still there, it doesn't seem nearly as confusing in this second book. Grant does a fantastic job of describing what objects (skin cells, a wound, the drain in a shower) would look like at the microscopic level. The scene with Bug Man trying to shower the nanobots off his skin is incredibly well written. And I still shudder when thinking of the hydra bots digging into Billy's skin.
With the first book, I also complained about the number of different characters and simultaneous storylines, and that's still an issue in this volume. In addition to the main story of Plath and Keats and the rest trying to stop Bug Man and Bukofsky, we also have a young Okinawan girl with OCD, a Scandinavian spy, a teenaged Lebanese hacker, Billy the Kid (no, not that Billy the Kid, a different one), and of course, the Armstrong brothers. Each of these characters has a separate storyline; granted, they all do appear to join up into a handful of main stories by the end of the book, but for most of the novel, I was wondering how each of these plots was going to be connected to the main story.
Normally, I loathe authors who insert (obligatory) romance into their action stories, but I can see the purpose here for Plath's and Keats's relationship - both are somewhat loners, not sure who to trust, and when someone can literally enter your brain (without you knowing it!) and mess with your mind to make you feel emotions you don't want to feel, you tend to question any feelings you may have for other people. It brings up an interesting point that runs through most of the book - how much of what we feel is true emotion or thought, and how much is being controlled or manipulated by someone else?
As I said, I did enjoy this book more than the first, and although it appears that Karen didn't put the third (and final?) book on her list, I do plan on going back and reading it when I get the chance.