Jack Vance 
Palace of Love [EPUB ebook] 

In the midpoint novel of the "Demon Princes" series, Kirth Gersen sets his sights upon the mysterious Viole Falushe. Vance describes this murderous creature as a "sybarite." "Sadistic pervert" would probably be a more apropos phrase. After several false leads, Gersen backtracks the villain to his point of origin – Earth, of all places! Then the trail moves outward again, to the starworlds and a place back of beyond where there is actually a physical Palace of Love.