I just noticed something else.
Clara snatched "Summer Falls" from the boy's grip and asked, "What chapter are you on?"
"Ten," said the boy.
Clara handed the book back. "Eleven's the best. You'll cry your eyes out."
Alright ... Moff likes to seed references to eleven throughout his episodes. But in this case, if Clara's line refers to the Doctor as the best, why will we cry our eyes out?
Something ominous is coming.