The central conceit uniting the stories is that humanity will colonize other planets not by adapting the environment of those planets to men (terraforming), nor by avoiding the environment of other planets (living in domes, say), but by adapting men to alien environments. By so doing, man will "seed" the stars. The first book tells of the beginning of this project. The main character, Donald Sweeney, is a young man who has been altered so as to be able to survive on Jupiter's moon, Ganymede. He has been raised completely alone, and told that his job is to infiltrate the criminal colony of Adapted Men already on Ganymede, and to bring their leader to justice. If he succeeds, perhaps he can become a true human, and live on Earth. It won't come as a surprise to learn that when Sweeney goes to Ganymede, his views change -- and that the genius scientist who is leading the Adapted Men has a visionary plan for man's future. The story is slightly marred by overly evil villains, and by a bit of silly science (not counting the wildly implausible "Adaptation" technology -- that impossibility I allow), but the overarching vision is wonderful, and the story is exciting and involving.

The next two books involve two different planets with radically different Adapted Humans. In "The Thing in the Attic," humans have been Adapted to live in the trees which dominated their planet. Over generations their society has ossified, held back by a fear of the ground, and by a reverence for the myths about the "Giants" who supposedly placed men in the trees. Honath is a heretic -- he doesn't believe in the Giants, and for that, he and several of his fellow unbelievers are condemned to exile and certain death on the ground, or, in their terms, in Hell. But after much hardship, Honath and a couple of his friends manage to survive on the ground -- only to make a shattering discovery.

In "Surface Tension," a spaceship crash-lands on a planet around Tau Ceti, a watery planet quite unsuited for even ordinary adaptations. The only solution the desperate crash survivors can see is to make adapted humans of microscopic size, to live in the tiny ponds that dot the planet's surface. The two episodes, one derived from "Sunken Universe," the other from the original "Surface Tension" novelette, tell first of the humans' alliance with some of the protozoans, and their joint battle against the more dangerous microscopic creatures; then, generations later, of the brave attempt of some of the humans to make a "spaceship" with which to travel to other "universes": i.e., to leave one pond and make their way to another. The concepts here are wonderful, and the ironic commentary is nicely handled, though the story itself is rather straightforward.

The final story, "Watershed," is set centuries or millennia in the future, and the wonderful twist is that now humans and Adapted men from all over space are returning to Earth -- to Adapt men to live on the environmentally ravaged hellhole that remains. Against this backdrop Blish tells a morality tale about the true nature of "humanity": it's a bit baldly put, but still well-taken.

This "novel" represents some of James Blish's very best work. He takes a striking idea and develops it fully, in the best tradition of pure Science Fiction. It's exciting and often inspiring: justly regarded as a minor classic of the field. Bravo to Victor Gollancz for returning it to print.