A lot of them have a bookplate in the front that says 'From the Library of Jurgen Leitner', hence the name. But beyond that, it is just a game of chance because not all of them are marked or the bookplate managed to last.
In most cases, they seem to have a common denominator of provoking an overwhelming sense of desire and dread in whomever is reading them. But generally if you're feeling that, it's already too late.