Keith Laumer 
Retief and the Warlords [EPUB ebook] 

Across the galaxies, against wrongdoers and rogues! Only Retief — the indomitable champion of the underdog and 27th-century diplomacy — can seal the peace between the battling earthlings and the lobster-like aliens known as the Haterakans. In constant peril, the daring spacewarrior must join a pirate band, cross the fatal boundaries of the Terran Defense League, and take on his arch rivals Foulbrood and Bloodblister. Facing certain torture, double-dealing, and ruthless espionage, he passes within inches of death. But he must emerge victorious — or the Hatracks will waste no time in executing their berserk plan to raise earthlings as a food supply!