's vision of life on Mars in this book is, from a scientific standpoint, way off, but the story he tells of two young men fighting to keep that life safe for their family and friends (with help from some of the native Martians along the way) is an interesting, funny, exciting, and wholly enjoyable one. There's even a bit of a mystery along with all the atmosphere and adventure. This is the sort of Heinlein book that one can't help smiling at the thought of.
Heinlein just has such a wonderful way of showing his readers a whole fully-realized world, including the technologies, social structures, culture, and everything else, without ever seeming to have any exposition. It's just all there, and we understand it by watching the story unfold.
This book is a really quick read, both because it's easy and short and because it's so fun and interesting there's just no reason to put it down.