Writing on both stone and lead was very common in the ancient world, although not necessarily to make books in the modern understanding. Stone inscriptions are of course very common, and there are plenty of famous ones like the Rosetta Stone. Lead is perhaps most well-known as the medium for curse tablets - small inscriptions aimed at attacking other people using supernatural powers - but other things were written on lead too, from letters to luggage labels. It's a really easy material to write on (believe me, I've tried), and would've been cheap and readily available in most parts of the ancient Mediterranean.

As I said at the beginning, neither of these materials would've been used to make books in the modern sense, but that's probably why Job mentions them in your passage anyway. He's wishing that his protestations of innocence would be written on durable materials so that they would last forever. By mentioning stone, he's also imagining that his words would be put up in public, so that they could be read by the whole community. That was ultimately the purpose of stone inscriptions - public viewing.