Elephant and Piggie, if you're not familiar, are early reader books (i.e., extremely limited vocabulary and low-density text) about the two best friends of the title. They are to be treasured, because they are adorably fun for adults as well as children—SteelyKid can rattle through them with ease, now, but the Pip also loves them to pieces, and they're wonderful for dramatic readings. (I went to our local used bookstore, hoping to get a stack of them, and couldn't find a single one of any of Willems' books. The library has an entire shelf of Elephant & Piggie that sometimes goes down as low as a couple of books.)
This was about an hour long and transitioned between, uh, at least seven of the books. [*] The Pip got a bit restless by the end, especially as the adaptation of We Are in a Book! to ...Play! involved audience participation, which he was not having any of (that's my kid), but on the whole it went down well with them. I liked it too, except the song they made of I Am Going!, because having Gerald (the elephant) not only sing at Piggie about how he doesn't want her to go but physically stop her is weird and creepy and yuck.
[*] I Am Invited to a Party!; Elephants Cannot Dance!; Listen to My Trumpet!; I Love My New Toy!; I Am Going!; Should I Share My Ice Cream?; We Are in a Book!. I am not entirely sure of the order of these.
With that caveat, recommended. And seriously, Willems is a treasure, you can't go wrong with E&P, or the Pigeon, or the Knuffle Bunny trilogy.