This is unusual for Heinlein in that the protagonist is not one his super-competent engineer types, but instead a down-on-his-luck actor. He is shanghaied by a spaceman, and soon find himself on Mars, being asked to impersonate a popular politician. His main qualifications for this is that a) he is an actor, after all; and b) he resembles the politician enough to pull it off. But because "The Great Lorenzo" has no technical skills at all, this book is about human nature and not science and engineering. This is middle period Heinlein, when he had mastered his trade, but before things got out of hand. This is a good read, and was the first of his books to win a Hugo award.