Tchaikovsky livens up the tale with intrigue, duels and menagerie of horrifying creatures... The scale of the story expands well beyond the confines of [prison drama], bringing in subterranean adventures, themes about class war and political corruption, and genetic engineering... Set in a dying world where death hovers impatiently over everyone's shoulder, Cage of Souls is a frequently grim read, but it's a compelling journey' SFX