Actually two books in one, plus a couple of essays. Covers the adventures of a crew of 18 inch centipedes on a planet with 300 times the gravity of Earth. Very interesting, if a little threadbare around human motivations (who can't really go exploring themselves, for obvious reasons), and heavy on the physics, chemistry, astronomy and just about all the hard sciences. Although there is one funny bit where they get out the sliderules, which just goes to show how technology has changed since the 1950s.