Double Star, Robert Heinlein, Ballantine Books, 1956, 243 pp
Lorenzo Smythe is a down-and-out actor with zero prospects when he gets recurited by a space pilot to impersonate an important politician. For real! Because the politician has been kidnapped by an intergalactic political group, an action which could lead to interplanetary war.
Using this wacky plot, Heinlein gets to comment on all sorts of issues: the ways of actors, the ways of politics, the political awakening of a self-centered person, etc. He also addresses the problem of achieving harmony between different species such as human beings and Martians, which gets into galactic racism and how people become racists.
I found the first few chapters supremely annoying because sometimes Heinlein was just a little too full of himself, but as always he won me over. In the end I decided that deep down, Robert A Heinlein had a good amount of respect for mankind (and Martians) and found potential for greatness in the most unlikely of people.
(Double Star is available in mass market paperback by order from Once Upon A Time Bookstore.)