Isaac Asimov Fantastic Voyage II: Destination Brain (1987)
I've had a patchy relationship with Isaac Asimov in the past. His prose was never conspicuously literary, tending towards emphasis on plot mechanics and the discussion of ideas; but on the other hand, considering he died with something like five-hundred books to his name - and we're not talking grubby eight page fanzines that no-one bothered reading - it would be pretty weird if he'd achieved that sort of word count without learning a thing or two.
Destination Brain is essentially Fantastic Voyage rewritten as Asimov wanted, with superior science and no concessions made to an existing film script, although I'm still not sure that the author's increased narrative freedom made for a better book. You can tell he had a blast writing the science, monkeying around with Planck's constant and related details of light, gravity, electrical force and so on, all in the service of a faintly plausible scientific means of miniaturising five people and their submarine; and the story itself - international politics, east-west relations, and how these impact on the life of a discredited scientist absconded by the Soviet Union - it's all lovingly told at a reasonable pace and with a level of emotional detail that one might not expect of Asimov; and he avoids making too many of those slightly weird references to women's knockers that have so unbalanced other works.
The only problem is that, given free reign, Asimov ended up writing about a hundred pages more than was really needed, so a novel that had the potential of a tense, well-written thriller actually tends to amble in places. The earlier version was certainly tighter, and although Destination Brain has room for improvement, it's nevertheless entirely readable and, I would argue, one of the man's better efforts.