... Yes, I think this may be the first cover where Harry isn't wearing a hat! ...
I suspect it's because it's a new publisher. "The Law" and "Out Law" don't use Roc/Penguin. I presume it's just easier all-round not to step on the toes of the artist who does all those novels, and their contract with Roc, etc etc etc.
Better -- as Jim isn't using those channels -- to do something wholly-different (I'm kind of hoping for Mirror Mirror to have a two-Harry cover, one hat-Harry & one hatless).