The idea of DNA computation is now widely known, indeed a limited form of such computation has already been carried out. Well brilliant gene scientist Vergil I Ulam has secretly been working on modifying the DNA within cells to give them a form of intelligence. When his clandestine research is discovered he faces losing all his work, so he injects the cells into himself. As you can imagine this is not a good idea! That is how Blood Music
begins, and in the book Greg Bear develops this scenario of what happens when intelligent microorganisms are let loose upon the world.
I would guess that this book might not be to everyone's tastes. The story can be somewhat disturbing at times. Furthermore, for much of the book there doesn't seem to be any central character - rather it is the story of a world trying to understand what is going on. Naturally it is all resolved at the end, but I would point out that this is only by getting even weirder. But if you're into this sort of science fiction then this is a must read, and I can see why is has won both the Nebula and the Hugo awards.