Very clever and the minimal use of color is beautiful.Even with so much going on, in the sense that this is like a puzzle for the reader, the design is still clean and comprehensible. The purple really makes the grey title pop (successful type hierarchy).
This book cover shows excellent figure ground/negative space. The contours formed by the position of the fox serve as the shape of a boy, I'm assuming "Peter." This empty space also creates a wonderful focal point for the book title to nestle into.