Mysterious Max — Megan Stine

A wisecracking ghost from the 1950s?
 
It's the fifth day of school and Jeffrey Becker is in trouble again! Jeffrey can't help it. He likes to tell a good story. The trouble is, his teacher calls those stories lies. And now he has to stay after school.
 
Jeffrey isn't the only one with the detention. When his teacher leaves the classroom Jeffrey realizes that he has company -- a ghost from the 1950s named Max. Max is one cool ghost, but he manages to get Jeffrey into more trouble than Jeffrey gets into on his own. And Jeffrey knows that no one will believe him when he says his new best friend is a ghost!