The Monster's Ring: A Magic Shop Book (The Magic Shop Books 1)

Twist it once, you're horned and haired;
Twist it twice and fangs are bared;
Twist it thrice? No one has dared!
 Russell is sure that the ring he gets at Mr. Elives' shop is just a silly magic trick, but he follows the instructions and twists the ring twice anyway--and becomes a monster! Includes an author's note.