I have your question, but I'm afraid I don't have the answer. I haven't the slighest idea what font is used. You might write to the publisher of both books , Scholastic, and ask them. -----Gordon Korman-----
Good eye, @Korman Junkie. Several recent Scholastic releases have used that handwritten block font plus a different specific font for “Gordon Korman” on the cover. I’ve wondered if it’s a graphic designer doing the lettering freehand because the text doesn’t register with font identifying apps. (I remember trying during one of the Kormaniacs Book Club discussions a year or two ago.)