This is the story of Winnie's life at eleven, running from her birthday until the day before she turns twelve, each chapter recounted a memorable event in each month. It's a story about being between things, having some friends go boy crazy and try to act grown up, while other friends hold back and act "babyish."
Myracle certainly has a good feel for what being 11 is all about. The problem really is that not an awful lot of interesting stuff occurs when you're 11, and this is really a series of anecdotes about being a tween. Good anthopology, not terribly gripping fiction. In other words, adults who want to be reminded what it was like to be 11 might get a kick out of it, but I can't imagine that middle readers would find the stories all that interesting.