There's been some web buzz about anthropodermic bibliopegy at Harvard this week. This Atlantic piece is a good example, offering some good images and quotes.
"On examination of the bookbinding, numerous follicular ostia are clearly visible and provide a raised, coarse texture to the front and back covers," Harvard dermatologist Vinod Nambudiri writes. "The pages are gilt-edged. The bookbinding has an even, golden-brown background hue."
"Focal areas of darker brown pigmentation likely reflect variation in the literal 'skin tanning' process underlying the binding’s production and consequences of handling over the book’s existence rather than melanocytic proliferations in the native skin based on examination with epiluminescence microscopy."