A sentimental grab on a recent visit to B&N as Crichton was my main man as a lad. The book was perhaps a third written when he died and was finished by another, but unfortunately much is still missing.
In the preface, Crichton makes a point about the unknowable complexity of nature, but the novel doesn't pursue this theme. It's instead "Honey I Shrunk the Scientists...On Purpose so Insects Would Eat Them" The stuff about microbots I found almost comical, in contrast to the suspense I remember feeling when reading about the nanobots in Prey a decade ago.
Characters were never Crichton's strong suit, but these are especially bad. This ends up mattering little, however, because virtually every character has been killed by the end. The villain is so ridiculous that I wouldn't have been surprised if he had tried to kill the micro-humans by frying them with a magnifying glass.
Had Crichton had the chance to finish the book, I suspect we'd have gotten more thematic meat to chew on. Here all we're left with is katydid steaks.