Ugh, I had my whole review here last night and GoodReads ate it. Last night's was far better written than this one. Sigh. 
 Willow has been seeing the school's ineffectual behavioral counselor because she is accused of cheating on a standardized test. (She got a perfect score, but it was due to her genius, not cheating.) She is out with said counselor and a new friend when her parents are killed in a car accident, and with no other family, her friend's mom takes her in (temporarily) until Social Services can find her a permanent placement. As "temporary" stretches into weeks, and then months, Willow finds herself belonging in a way she never has before--and she's beginning to bring out the best in the people around her as well. 
 This is a little Magical Fairy Tale for my tastes, but as a Triumph-Over-Adversity summer-reading type book, it's excellent. The reader is reminded of Willow's grief from time to time, but mostly she seems to be okay, like her parents are on an extended vacation and she barely gives a thought to her old life (except that she misses the garden behind her old house). Naturally she brings out people's willingness to help, and makes them better people, because that's what kind of book this is. 
 It does have a multicultural cast (Willow is mixed-race but adopted, so we don't know her background; her friend's mom is Vietnamese and their father was Mexican; the taxi driver is Latino), which gives it points in the Summer Reading column. This is the kind of book that adults will wet themselves over and middle-schoolers will pick up because they have to, though they'll probably enjoy it once they do.