I must have read this first in the 60s (it was first published in the 50s), so coming to it again, it was almost, but not quite, like reading it for the first time. A couple of Heinlein's perennial themes come through - love of cats and engineering, the hero being a cat-loving engineer. Despite being neither or these, nor, indeed, particularly heroic, I enjoyed the book. It is set largely in 1970 and 2000, neither of which is at all recognisable to those of us who have lived through them - a constant problem with old sf. I suggest you assume it took place in a parallel universe where many things are significantly in advance of our universe, but some things, communications and much of computing, for example, are far behind. The hero in 1970 invents what are, to all intents and purposes, domestic robots, is cheated out of his rights, goes into cold sleep, wakes 30 years in the future, travels back to 1970 invents some more, goes back into cold sleep, gets the girl and lives happily ever after. We also get some interesting comments on time paradoxes. Does this précis do justice to the book? Of course not. Although by today's standards it is a rather short novel, it shows that Heinlein is beginning to develop the style that later led to his major works. Interesting from that point of view, but, above all, a good read. Get it.