The fourth book in the series about the Cassons by Hilary McKay.
Seriously. Read these, or something. Start with Saffy's Angel. I won't say much about the plot, since it's the fourth book. Although I suppose I could tell you that Indigo uses his mad skills to great advantage. Also, when you're all done reading them, the fun doesn't have to end! No, no! Cuz Rose has a blog. Yessss!
In all honesty this one was pretty anticlimactic to me. But I'm sure (positive) that is only because I read the last one (Forever Rose) first. And this one is next to last. So.
Link to my previous Casson reviews.