The newest Knuffle Bunny book by Mo Willems. It's called Knuffle Bunny Free: An Unexpected Diversion and is on-order and due to arrive any day now! There are two others in the series, Knuffle Bunny: A Cautionary Tale and Knuffle Bunny Too: A Case of Mistaken Identity [both JP WIL]. Sadly, Knuffle Bunny Free will be the last book in the series. Mo Willems explains why in a recent Publishers Weekly interview.
If your favorite little one is a Mo Willems fan, check out GoMo. There you'll find games, short videos, and, the opportunity to win a life-sized Knuffle Bunny for your very own. If you're a fan, check out Mo's blog, Mo Willems Doodles.