I was meh almost the whole episode - I didn't like that the Frozen bits were taking the movie as straight up exactly what happened, when every other fairy tale and such changed the background/past to be more suited to this genre. Otherwise it was fine.
I did feel like much of the episode was a little on the nose - just, very lacking in subtlety. I was almost ready to write it off until the last 5 minutes - I'm interested in the idea of where the book came from, even if Regina's reason is stupid.
As for the hat, I'm sure it won't be Mickey - if anything, it would be Yen Sid, the person who actually knows how to use it. And isn't a mouse.