UNDERGROUND comics legend R. Crumb is playing some of the devil’s music in the Hamptons before hitting the road to promote his latest work about God’s own creationary chops, “The Book of Genesis Illustrated.” Crumb, a longtime blues lover who plays the mandolin, will be sitting in Saturday night with the East River String Band at Stephen Talkhouse in Amagansett. The artist is tight with East Village band members John Heneghan and Eden Brower, and even drew the cover of their upcoming CD, “Drunken Barrel House Blues,” which rolls out on Halloween.