Blending biography and archival history, After the Flood asks of Bob Dylan, “If your dreams are fulfilled at twenty, what do you do with the rest of your life?”

A familiar narrative goes: Bob Dylan, the voice of sixties counterculture, disappeared in the 1970s, then released arguably the worst music of his career in the 1980s—only to be resurrected in 2016, when he was controversially awarded the Nobel Prize in Literature. Dylan’s concerts once began with an announcer intoning a deadpan versi...