"Gunner Cade" by C.M. Kornbluth and Judith Merril
"Gunner Cade" was first published in 1952. The authors will be familiar to those versed in sci-fi's Golden Age (the 50s), though their names are far from common knowledge today.
This book is only 160 pages long, and it's a straightforward action-adventure piece, so there's little I can say about it. It's set in the future, Cade is a member of a warrior caste called the Armsmen, and there is a plot involving Earth, Mars, the Emperor, and a high official called the Power Master.
It's a solid, entertaining book that doesn't ask much of the reader. I thought it was good, but not spectacular. It would make a decent movie, though they'd probably have to add a few subplots, and amp up the sex a bit. The main character spends a fair amount of this book in a brothel, so that wouldn't be a difficult thing to do.