Well I watched the documentary. If you are a blues fan it’s worth the watch but as for getting deep into Johnson they missed the mark. They brought up a couple things I hadn’t yet know and touched a bit on his playing style. He may have been using his thumb on the fret board to make that sound he was able to make that sounded like two guitarists playing. There are only two known pictures of Johnson and no video footage. If you are a blues fan it’s worth the watch but if your already into Robert Johnson not much new info revealed.