Paul McCartney is branching out from being one of the greatest songwriters of our time to a children's book author with the release of Hey Grandude! this fall. The Beatles legend is too cool to just be called grandpa, opting for grandude after one of his eight grandkids referred to him by that name. McCartney reveals the picture book story sets off a magical adventure, with the title character taking the kids through stampedes and avalanches while riding flying fish. Pre-orders are happening now for the September 5th release date.