Not a sequel to the original Fantastic Voyage (a 1966 movie novelization), which Asimov chooses to ignore completely; the upshot isn't too much more than a sclerotically talky retread. In the 21st century, the superpowers coexist peacefully--so why do the Russians choose to kidnap frustrated brain researcher Albert Morrison (no one believes his advanced theories)? Well, genius scientist Shapirov, the inventor of miniaturization, lies in a coma, the victim of an experimental accident; the Russians need Morrison's expertise in order to tap the thoughts of the dying Shapirov (he was on the point of a dramatic breakthrough). The problem is that Morrison doesn't believe in miniaturization and, indeed, is terrified at the prospect. Still, after some judicious blackmail, he agrees to enter a specially-built submarine, along with its stereotyped crew, hearty Dezhnev, manipulative Boranova, Finno-Russian Kaliinin, and obsessive Konev: they will be shrunk to molecular size and injected into Shapirov's comatose brain. After various adventures--unsurprising stuff to fans of the first Voyage--they reemerge, the mission apparently a failure and Shapirov dead, with a mildly surprising twist ending still to come. Like much of Asimov's recent output: a novel-sized conversation, scientifically more credible than FVI but just as tepid plot-and-drama-wise. It slips down easily enough but leaves no lingering impression.