Scientists took various samples from the covers of three books suspected to have part or whole covers comprised of human skin and tested the samples using peptide mass fingerprinting to identify the binding's source. Though two of the three volumes were made from sheepskin, Houssaye's book is most definitely human skin. Further testing determined the cover is comprised from the skin of an unidentified French woman who died suddenly in a mental hospital.
Interestingly, researchers doubted the cover's composition despite the fact the book had come with a note stating the cover was made of human skin:
"Ce livre est relié en peau humaine parcheminée, c'est pour lui laisser tout son cachet qu'a dessein on n'y a point appliqué d'ornement. En le regardant attentivement on distingue facilement les pores de la peau. Un livre sur l'Ame humaine méritait bien qu'on lui donnait un vetement humain: aussi lui avais je réservé depuis longtemps ce morceau de peau humaine pris sur le dor d'une femme".
"This book is bound in human skin parchment on which no ornament has been stamped to preserve its elegance. By looking carefully you easily distinguish the pores of the skin. A book about the human soul deserved to have a human covering: I had kept this piece of human skin taken from the back of a woman."
Although it seems crazy to think of books bound with human skin, the practice, anthropodermic bibliopegy, was actually quite common. The earliest known example is a French Bible dating back around the 13th century and the practice continued into the 19th century.
Additionally, Harvard is not the only university to contain examples of anthropodermic bibliopegy, but only one of many libraries; for example, Brown University's John Hay Library boasts three human skin covered volumes and Dale Carnegie's book, Lincoln the Unknown, has a patch of skin on its cover from a black man embossed with the title.