Did he understand those books? Was he able to present the premises, propositions and arguments from those books or just to recite them?
The latter does not constitute even knowledge, just memory.
So, we don't tend to remember facts for the sake of facts. This obviously isn't always true, but for vast amounts of information, it would be very difficult to remember single "nodes" of information without having some connection to other information.
Memory contestants use this to their advantage, by creating some sense of story and/or place to attach the otherwise arbitrary information, like digits or cards, to.