It's a Todd Haynes film, and it's around and about Bob Dylan. It's a twisty beast of a biopic and it's going to infuriate a lot of people - particularly hard-core Dylan fans who have a lot of versions of Dylan here to dislike, many of which will probably come across as parodies to the extremely well informed and non of which are going to necessarily conform to their particular preferred version.
You get seven ages of Dylan, played by six actors:
Woody Guthrie (the 14 year old Marcus Carl Franklin) - Dylan's imaginary youth as orphaned black hobo
Arthur Rimbald (Ben Whishaw) Dylan as uppity symbolist poet national security threat
Jack Rollins (Christian Bale) Dylan as truth-singing folk star
Robbie Clarke (Heath Ledger) as famous womanizing actor and rubbish husband
Pastor John (Christian Bale again) Dylan as sincere 1970s evangelical preacher
Jude Quinn (Cate Blanchett) Dylan as cynical, drug addled Rock and Roll star
Billy the Kid (Richard Gere) Dylan as post-66 exile
Haynes seems to be having a whale of a time grappling with the thorny task of representing genuine, massive celebrity, wisely dispensing immediately with any pretense to be uncovering the truth about his subject. Instead he cycles through the most popular myths about Dylan (and not necessarily in chronological order), ending up in a town full of masked and costumed characters. Richard Gere's Dylan may be conceptually the strongest character in what turns out to be a Dylan themed Masque, unfortunately he also turns out to have the least interesting stuff to do and say.
Christian Bale's return from the wilderness of disillusionment as Pastor John has got to be my favorite Dylan, and the short segment is Haynes at his observational best. Cate Blanchett, as the snake hipped, electric haired and newly electrified Dylan is the star performer here though. She really manages to channel her experience of the insanity of celebrity through Jude Quinn, despite having some of the most cringe-worthy moments of the whole movie to deal with. Particularly noteworthy for sheer crass embarrassment is the literal montage to Ballad of a Thin Man, but unfortunately that isn't only the only heavy handed note in her sequence. Her performance is incredible though.
Dylan granted Haynes rights to use his music in the movie, and in the end it's clearly the soundtrack which plays the starring roll here - precisely as it should be.