Cloud and wallfish - Anne Nesbet

"An atmospheric page-turner. . . . Edgy, dramatic, and emotionally rich historical fiction that provides a vivid look into an extraordinary moment in history." -The Horn Book(starred review)

One ordinary day, Noah's parents tell him his name isn't really Noah, his birthday isn't really in March, and his new home is going to be East Berlin - on the other side of the Iron Curtain. East Germany seems the least likely place in the world for a kid from America with a lot of secrets of his own (and an Astonishing Stutter) to make a friend, but then Noah meets Cloud-Claudia, the lonely girl who lives one floor down. Noah and Cloud-Claudia have only a half-imaginary map and a shared fondness for codes and puzzles to guide them in a world where walls - and the Wall - are closing in.