Memnoch the Devil by Anne Rice The Vampire Chronicles #5
 
In the fifth Vampire Chronicle, Lestat is searching for Dora, the beautiful and charismatic mortal daughter of a drug lord. Dora has moved Lestat like no other mortal ever has, and he cannot get her out of his visions. At the same time, he is increasingly aware that the Devil knows who he is and wants something from him. While torn betwen his vampire world and his passion for Dora, Lestat is sucked in by Memnoch, who claims to be the Devil himself. Memnoch presents Lestat with unimagined opportunities: to witness creation, to visit purgatory, to be treated like a prophet. Lestat faces a choice between the Devil or God. Whom does he believe in? Who does he serve? What are the element of religious belief? Lestat finds himself caught in a whirlpool of the ultimate choice
 
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