#1-8 have glossy paper interiors and a unified design with a blue and white spine with blue and black letters with no character illustration on the spine. #9-10 have matte paper interiors and have a different design with a black spine with white letters with a character illustration at the top of the spine.
#1-10 are trade paperbacks. #11 is a hardcover. Starting with #12, the series reverts to trade paperback.