Walpurgis III

While this isn't exactly an epic book, it's still one hell of a fun read. You'll easily be able to finish it in a night or two, but parts of it will stick with you for years.

Conrad Bland has finally found a world that accepts him. Bland is a man so evil that evil needs to be redefined to describe him. Having perpetrated atrocities on several worlds, he finally comes to Walpurgis III. Here, where Satanism, witchcraft, and black magic are the norm, many hail him as a hero, and he revels in his freedom to torture and murder. But, not everyone is so enamored of him, and they have dispatched the galaxy's best assassin to terminate Bland. Detective John Sable picks up the trail of the assassin, and must decide whether to stop him, or let him continue with his mission. He will be forced to face his own inner fears and demons, and make an irrevocable choice, for good or evil.