Vitals by Greg Bear.
Average bio-tech thriller, much in the vein of Michael Crichton or Bear’s own Blood Music (which is better). It’s the Manchurian Candidate meets Blood Music. There are similar thoughts on the intelligence of bacteria and its ability to communicate with its intelligent host — I’ll never quite be able to look at intestines in quite the same way. The dust jacket blurb mentions a search for immortality, but it’s a MacGuffin — the actual plot jumps off into paranoid cellular conspiracy soon enough, dragging in Stalin and Beria for good measure.
It’s a page-turner, and Bear has learned a few new tricks: the plot jumps back and forth in time, telling the story through two different protagonists. The two stories are quite linked, and events in one show up in the other soon enough. Definitely makes for a more interesting read.
Good for a plane ride, but nothing worth keeping to read again.