The Devils Book 1: The Devils Gollancz (370614117)

Europe stares into the abyss. Plague and famine stalk the land, monsters lurk in every shadow and greedy princes care for nothing but their own ambitions. Only one thing is certain: the elves will come again, and they will eat everyone. Sometimes, only the darkest paths lead towards the light. Paths on which the righteous will not dare to tread . . . And so, buried beneath the sacred splendour of the Celestial Palace, is the secret Chapel of the Holy Expediency. For its congregation of convicted monsters there are no sins that have not been committed, no lines that will not be crossed, and no mission that cannot be turned into a disastrous bloodbath. Now the hapless Brother Diaz must somehow bind the worst of the worst to a higher cause: to put a thief on the throne of Troy, and unite the sundered church against the coming apocalypse. When you're headed through hell, you need the devils on your side.