Ahh yes, a book about a cupcake. Can't say that I've ever heard of one before, and that's a good thing. New and different; that's what I like. Sure, Cupcake is basically a story teaching the reader that being plain and different is ok, and that has been done before, but never with a Charise Mericle Harper twist. The lesson doesn't hit you in the face. You don't read her books expecting to learn something; you read her books anticipating enjoyment and a funny ending - the learning part is a bonus that may (or may not) dawn on you later.
The other thing I enjoy about Harper's work is that I cannot look at a book and say "ahhh yes, I can tell by the artwork that is a Charise Mericle Harper book". Nope. Her style is varied and there is no way you would confuse Fashion Kitty with Mimi or even Lulu. That may or may not be such a good thing to an artist, but to me, a simple Children's Librarian, I enjoy stories more when the pictures actually match the text and I admire flexibility in people. It shows a willingness to enjoy new things as well as the ability to express oneself in more than one way, not to mention the fact that because of her long list of writing and illustrating credits, she is sure to have a book to suit just about anyone.
Cupcake is a great fit to the 4-8 crowd (share it with a Fancy Nancy fanatic to remind them that plain is ok too!), though I bet the adult sharing the book with a young child will enjoy it just as much. Be warned though: reading the story might make you want to bake cupcakes, but guess what?!? A recipe for that very purpose is included in the back. YUM!