Hardback book.
"Felix is supposed to guard the wall-- everyone knows that horrible monsters live on the other side. But it's a pretty boring job, so he spends most of his time day-dreaming about playing in a band. Then one fateful day, he hears music coming from the top of the wall, and that changes everything! Get ready for an epic jam session-- 1, 2, 3, 4! With bold, joyful art, this timely, humorous story celebrates the joy of opening yourself up to the unfamiliar and music's power to bring us together."