So who thinks the people who have been "saved" are trapped in the books?
I've also heard a theory (not an actual spoiler, but a genuine theory) that the little girl (who I think has to be CAL) is actually a young Professor River Song.
Personally, she really got on my nerves a bit by the end (Don't want the Doctor to read about his future? Then don't leave the book sitting around for him to find! Don't want to give away spoilers for the Doctor's future? (And how funny were all the references to spoilers, anyway?!) The don't show him your SONIC SCREWDRIVER!) and I'm wondering if perhaps she might kick the bucket next week in some tragic way that makes the Doctor feel as if he owes it to her to go back in her personal timeline and meet her and ask her to travel with him, since they were obviously close. That comment about his eyes being so younger makes me wonder if maybe the older him knows he is going to lose her in the Library all along....wibbly-wobbly, timey-wimey STUFF!
Just a theory.

Can't wait for next week!!