A collector is given the opportunity to purchase the skull of the Marquis de Sade.

"Christopher Maitland sat back in his chair before the fireplace and fondled the binding of an old book. His thin face, modeled by the flickering firelight, bore a characteristic expression of scholarly preoccupation. Maitland's intellectual curiousity was focused on the volume in his hands. Briefly, he was wondering if the human skin binding this book came from a man, a woman, or a child."

Weird Tales (September 1945)
Bogey Men (1963)
The Skull of the Marquis de Sade (1965)
Complete Stories of Robert Bloch -- V 1: Final Reckonings (1990)

Adapted for the film The Skull (Amicus, 1965).

Comment: Another tale of an obsessed collector is Bloch's The Man Who Collected Poe.