The most interesting thing about this one was that there were three children this time instead of only William. And Ms. Winthrop did an admirable job of outlining their differences without making any of them seem either better or worse than the others.
Jason is the typical reckless, sports-minded, too-brave-for-his-own-good young man. William is more reflective, less susceptible to peer pressure, and more open to wonder. Gudrin is redemption for females in a lot of classic fantasy. She still cooks for everyone when they're trapped in the dungeon, but she's learned to read and write and she learns to ride William's bicycle.
I like that no matter the child reading, they will likely be able to find someone to relate to.
I wish it had been explicitly stated whether the giant rat had really come from the attic. It was nicely implied, but I couldn't help wishing that part of the resolution had included discussion of its true origin.