Across the Green Grass Fields

I think every series has its “waiting room” books or episodes where the author kind of plays around in the world without really moving the main plot forward. Here we get a stand alone story of Regan and her horsey world. Cue My Little Pony. Is it good? Sure, everything McGuire writes is good. Does it give us cameos of our favorite characters from the series (Christopher FOREVER!), no.
As I listened to this on audio, and it was a mere 4 hours long, I was just grateful to go through a portal and learn about a world unlike my own.