You aren't supposed to take pictures in the library, but I managed to get two before being stopped by a French ninja librarian.
Founded in Charles V in 1368 at the Louvre, it was opened to the public in 1692. Woot!
By 1925 it had 4,050,000 volumes and 11,000 manuscripts.
It's a very impressive space, particularly the Richelieu site, as official photos reveal: