If I Were You, by L. Ron Hubbard
Book Description
Circus midget Little Tom Little is the king of midgets, loved by crowds and carnival folk alike. Only he doesn't just want to be a bigger circus star, he wants to be just like the circus' tall and imposing leader.
Trouble begins the moment that a set of ancient books containing the secret of switching bodies finds its way into Tom Little's tiny hands. When he magically trades his small frame with that of the circus chief, he finds himself in a giant-sized heap of trouble - his craving for height has landed him smack in the center ring surrounded by forty savage cats!