It's hard to say when the book doesn't give any references. (I looked at the entry on Google Books.) You'd've thought somebody besides M. van Scott would've mentioned these big old books being called agrippas. She probably just made it up. Is it supposed to be in English books? I looked at large online German (Grimms) and French (Treŕsor) dictionaries but found nothing.

[Addendum: While googling about on this topic I came across the term for binding books in human skin: anthropodermic bibliopegy. Top two results: the Wikipedia article on the topic and an article, much linked to on the web, of books in some university libraries.]

Ceci n'est pas un seing.