The Library of the Damned — Jeri Westerson

Leopold Kazsmer, stage magician extraordinaire, must make the dangerous journey to the Library of the Damned, a structure fluctuating between the worlds and filled with the archives of the centuries, to find a way to rescue his father and save his own soul from the Unholy Hosts with whom he has made a deadly covenant and who have trapped his father in the darkest depths of Gehenna for seventeen years. With Leopold's amazing cadre of friends—the Special Inspector from Scotland Yard Mingli Zhao, the imp Suchah, the ghost of Inspector Thacker, the automaton Raj, and led by Leopold's daemon friend Eurynomos—London goes to war with Gehenna, and all hell literally breaks loose in this final chapter of the Enchanter Chronicles.