If you don't know the story - well, that isn't a surprise. In the 1950's, poet Allen Ginsberg wrote and published Howl, a epic beatnik poem. There was a famous San Francisco trial that put the publisher on trial for indencency. FYI - the words used seem almost quaint in the era of RAP.
This is kind of the landscape of the movie, but that isn't the story. The story of Howl is the poem of Howl, read by James Franco, intersperced with interviews with Allen Ginsberg (again, Franco), cuts from the trial (with Jon Hamm and David Strathorn) designed to add depth and background to the poem, which floats in an out (and doesn't ryhm, but has a candence that is mezmerizing).
The poem is illustrated, sometimes by animation, sometimes by the actors sometimes by light. It is not a movie to have on in the background. It slowly pulls you into a sphere that is wonderous.
It was cool.