The latest book in Willems' series of early readers about a piggie named Piggie and an elephant named Gerald, June's Can I Play Too? (Hyperion), is a typically strong entry. The conflict the two encounter in this volume is entirely delineated in the title and cover image.
The pair are going to play catch—Piggie loves playing catch with friends!—when a snake slithers up to them and asks if it can play too. Which leads to some rather awkward exchanges:
The snake busts their chops for a bit, forcing them to explain why they think it can't play catch, and then they all give it a shot. Can a snake play catch with two friends who have arms? How?
The resolution is pretty amusing, and the little kids I read it too liked the snake's not-having-any-arms joke and first few attempts at playing catch, but I enjoyed the awkward humor, and, especially, all of the opportunities the uncomfortable social situation gave Willems to act through his characters.
I'm used to his amazing versatility with Piggie, Gerald and the pigeon's relatively blank, abstract faces, but what he was able to accomplish with the snake was really something, as it has even less detail to its design than all those other characters.
So, in summary, Mo Willems is still awesome, and his Elephant & Piggie series remains an awesome showcase for his particular awesomeness. If you haven't already, you should read it—and all the previous ones. They're basically hardcover comic books, with each page functions as splash-page panel.