The clue, of course, is in the title, a steal from Steinbeck's `Of Mice and Men' and relevant in the sense that the place of the mice in the original title has been taken by men.
In this novel, following a sudden and devastating attack and invasion by `monsters', men are now in the place of mice, reduced to the status of parasitical vermin, living in the air pockets of the insulating material of monsters' houses.
The monsters are enormous brontosaurian creatures with a ring of prehensile tentacles around their necks which serves them as fingers.
The central figure is Eric, known as Eric the Only as he was born a singleton, rather than part of a larger litter. Eric is about to go on a rite of passage ritual to steal from the monsters, after which he becomes a man.
However, Eric soon finds himself caught up in a war of ideologies. His tribe believe that that they should be trying to recreate Ancestor Science in order to defeat the invaders while others (Eric's Uncle being one of them) believe that Man should be using Alien Science to fight the creatures.
Unbeknown to Eric on his quest, the chief has discovered his uncle's heresy and has called in reinforcements from neighbouring tribes to put down the rebels.
Eric is captured on his return but manages to escape and returns to the burrows of the Strangers. eventually he is captured by monsters who are experimenting with methods of extermination. Eric has heard tales of the Aaron people, a tribe far more advanced than his own `front-burrow' tribe. He is imprisoned with Aaron female and Ray the Runner from his old tribe. With her help they escape and manage to return to the Aaron people, and Eric is let in on the Aaaron People's secret plan.
It's a refreshing and welcome change to see humans reduced to existing as an inferior species, but nevertheless finding a means to adapt and survive. There's also a nod to the concept of sexual equality with Eric's feisty Aaron Lady preaching a form of feminism which doesn't go as far as it might have sadly, but is surely better than the simpering heroines of yesteryear.
It's a deceptively simple book which manages to illustrate the dangers of organised religion with its tendency toward fundamentalism, rigid dogma and inflexible rules, as well as overturning our arrogant notion of Humanity as masters of the universe. It is very likely, as Tenn suggests, that we are very very far from being anything of the sort.