I just completed the quest "History of the Cabal". It would be awfully nice to be able to re-enter the Schism Reading Room later and/or re-read History of the Schism. Blocking this off from characters that have completed the prerequisite quests seems like a waste of a beautiful room.
Continuing on that subject, the assembled books/runes/etc of the various worlds would be more useful if they could be later read after their respective gathering quest is completed. I don't see a benefit to disabling them after they've been read once.