Plot: the sun is about to get really, really nasty. All water will be boiled off. Earth will be uninhabitable, so it's time to send some folks to Mars. Review:

Once our ship gets out and into space, the passengers discover it is too well insulated; they are slowly being roasted to death by their own body heat, until they take a couple of insulating panels off. Gee whiz!

At the time of the story, the author would have us believe, we have been in the spaceship business for some years; we've got a colony on Mars and regular, if infrequent, passenger service thereto -- and all this time, nobody had figured out a way to regulate the interior temperature of spaceships, untl this very moment? Really?

Well, the middle of the book is always the tough part.