What if books were used as two-factor authentication. You could choose a book from your shelf and enter it's title, print date, and publisher into Google or some other site. Then, when you went to login, it would ask you what the first twi words on the eighth page are, for example. Because the website knows the exact copy of the book you're reading, they know where the words are.
This works because the word(s) can be random each time. There aren't "infinite" possibilities, but there could be more complicated combinations. "What is the first word of the book and the second to last word of the book?" Because the login page wouldn't tell you the name of the book, someone trying to hack your account wouldn't know what book the website was talking about.