Take the book to Milton, he’ll know.
Milton, of course, virtually creams when he sees the binding. He knows that it’s not leather; not from a cow, anyway. He accepts it into his hands like it’s a Fabergé egg or a fragmentation grenade or both. He turns it over slowly, gingerly, whispering, “It’s in magnificent condition.”
I can read Milton easily, even without telepathy. He knows it’s dangerous, but he still wants it desperately. I offer to sell it to him for a price he can barely afford; I’ll come back to reclaim it from his dead hands tomorrow night.