Concert posters, as any rockologist will tell you, are the Van Goghs and Matisses of the music scene. And in 1987, author Paul Grushkin cobbled together an encyclopedia of the genre's best in an eight-pound hernia of a book called "The Art of Rock." In the 17 years since, the rise of graphic-art technology, digital music and local indie-rock scenes has sparked a second wave of eye-popping posters. So Grushkin and collector Dennis King teamed up for a sequel. "When you've got the Bible," says Grushkin, "there's gotta be a New Testament, right?" Hence, "The Art of Modern Rock": an exhilarating volume of 1,800 posters from grass-roots artists hyping local shows by bands like the Beastie Boys, the Flaming Lips--and many more no one's heard of. Like its older sibling, it flat-out rocks.