Auggie and Me

If you read Wonder, then I would recommend reading Auggie and Me by R.J. Palacio as well.  It is not a sequel to Wonder, but a companion explaining different perspectives of Auggie's first year at Beecher Prep.  Written in first person, Julian, Christopher and Charlotte tell their story in regards to Auggie.  The author wrote it as if you had recently read Wonder, and since I read it over a year ago,  I had forgotten some of the characters.  Labeled a companion book, you would need to read the other book in order to make sense of this one.