It takes several days for a villager (librarian) to resupply rather than the intended twice a day. Some villagers have still not resupplied a single time after a few in-game weeks. They many lecterns and bookshelves nearby. Specifically one for each.
Environment
Java (build 1.8.0_201-b09)
Up to date on Windows 10
Pre release 4 server
Duplicate of MC-147740