I read this book in my younger days (back near the stone age…). I call my journey “Troopers in reverse order”, because I didn’t read Starship Troopers by Heinlein until years later. Heinlein’s was more of a social statement, and Farren was more action/individualist. It is a very “big picture” read with intense one on one action.
The publisher says:
“Their Master’s War” Is a thrilling, tough, Militaristic SF jaunt in the Harry Harrison, Robert Heinlein vein. The group of young, primitive, virile men and women are sent by their tribal elders to be received by the “GODS” who are making mysterious ans imperious demands upon those who are sentient. The Gods turn out to be huge spacecraft, which transport the groups into their metal maws, the inhabitants of which commencing a brutal program of re-educations on the hapless and bewildered recruits.
The spaceships are controllers by the Therem Alliance, a military society wedded to the ethics of constant war with everyone else in the universe and the new recruits are just another load of battle fodder as far as they’re concerned. The story focuses on the plight of Anah 5 and the exceptionally tough, hard drinking, brawling division of nutters and how they will change the direction of humanity under the yoke of oppression.”
You can follow the link to the Amazon page and read some of the reviews. it has a pretty supportive group. A fun read.