It'd be easy for this to contain more words than the actual book -- so I'll try to keep it short. Henry's got a little bit of money, and doesn't want his little sister to get it. So he sets up a series of elaborate traps and challenges (think Raiders of the Lost Ark meets Home Alone) to keep her from it.
Along the way, his imagination his on full display and he eventually learns something. There's a very sweet ending that will hopefully teach by example.
I cannot say enough good things about Wen's artwork. It's adorable. It's dynamic. It's simple, but eye-catching. It doesn't detract from the story, but shapes and propels it. There's not a lot of detail, but what's there is important.
For the younger set, I can't imagine how this won't become a favorite. Thankfully, it should be pretty easy for parents to re-read. Amusing story with great art. That's pretty much what you're looking for in this kind of book, right? Available in hard copy and e-book, it's a great buy.
Disclaimer: This book was provided to me by the publisher in exchange for my honest opinion.