After R. J. Palacio’s “Wonder” was published in 2012 and became a middle-grades juggernaut, many hoped the author would continue the story of August Pullman, the Manhattan boy born with serious facial deformities, and his friends and family. “Wonder” ends as Auggie is finishing fifth grade at Beecher Prep, his first year in school after being home-schooled for the surgery-filled first decade of his life. He is given a special award recognizing his courage by the school’s principal. But then what? Palacio’s characters were hard to say goodbye to, and in the current series-heavy world of children’s books, it seemed natural that there would be more to come.