As the parent of boy-girl twins who just turned five, and as a reader, and as the owner of a bookstore, I can tell you that there are two kinds of books for kids that are sadly uncommon:
1) The innovative. Well, there are innovative books, like Gallop! But an innovative book that 5 year-olds love, that's rare. To that end, we are pleased to be selling copy after copy of Press Here by Herve Tullet (Chronicle Books, $14.99). It's a big hit at our preschool: an interactive book of a magical sort. You just have to come in to see it.
2) The truly funny. And I mean funny for the kids and for the grown-up reading it. We just received our first batch of Betty Bunny Loves Chocolate Cake by Michael Kaplan and Stephane Jorisch (Dial Books, $16.99). When Betty Bunny discovers chocolate cake for the first time, she decides she loves it so much, she's going to marry it. Instead, she makes do with carrying it to school in her pocket. We love Betty Bunny.