Of Men and Monsters (Gollancz SF Collectors' Edition)

Giant, technologically superior aliens have conquered Earth, but humankind survives - even flourishes in a way. Men and women live like mice in burrows in the massive walls of the huge homes of the aliens, scurrying about under their feet, stealing from them. A complex social and religious order has evolved, with women preserving knowledge and working as healers, and men serving as warriors and thieves. For the aliens, men and women are just a nuisance, neither civilized nor intelligent, and certainly not a worthy adversary. In fact, they are regarded as vermin, to be exterminated.