The newest chapter of A Balance of Fire and Light

The disaster that had been left in Twilight's castle has been mostly cleaned and is now ready to be sorted and put away.
Mostly.
Talking with Starlight, Twilight reveals that not everything has been accounted for. If it were just a reference guide or a text book about magic, that would be one thing, but these were a bit more important.
What's gone missing?
Who has them?
Why were they taken?
In the next chapter: Derpy crashes into a mail box, Spike and Starlight sell candy, and Twilight has a breakdown.