I'm seeing a lot of positive reviews of this episode and the season in general, which makes me happy because I enjoyed the books.
That being said, I'm actually a little disappointed in the way they rushed a lot of things this season. I think there was enough material to stretch Book 1 (let alone Book 2 and Book 3) out to two or three seasons, and they not only crammed all of Book 1 into 13 episodes, they even got most of the secondary plot of Book 2 crammed in as well... such a waste of a lot of the plot points and character development.
I did like many of the changes from the book, it kept me guessing. The Plover misdirection was well-done (if telegraphed), and the elimination of the rest of the Chatwins was probably a wise choice as well. The introduction of Kady was confusing at first but now that we know she becomes Asmodeus, it's brilliant. She'll definitely be back next season. Penny's character was probably the best stand-out change for me, much more fleshed out than in Book 1, so I'm also looking forward to the inclusion of some more of his storyline sans-hands. Elliot was the best cast, and brought his character to life.
So I guess my main complaint is the lack of detail on the elements that they did choose to keep. Without going into spoiler territory, Book 1 takes place over the course of 5+ years, so there is definitely room for exposition if they had chosen to do so. This is the same complaint I have about the "Ender's Game" movie adaptation, where they cover 6+ years worth of plot in a 90 minute movie. It gives the impression of an accelerated timeline, and really changes the stakes.
We missed a lot of cool things from the books that would have been awesome to see on screen. They could have spent several episodes on the overall Fillory portion of the Beast, not just this one episode. In the book, they didn't know they were going to find the Beast, whereas in the show they were explicitly searching for him.
~Tighr: Not helping the situation since 1983