John Darnielle may be best known for his band The Mountain Goats, but he's also the latest blogger with a book; this weekend he's in town as both a musician and an author. Tomorrow night Darnielle will read from his book, the latest in the 33 1/3 series, about Black Sabbath's Master of Reality; which he wrote through the voice of a 15-year-old boy who's been institutionalized. Before taking a seat at Housing Works on......