The Allen Ginsberg biopic Howl is a curiously unconventional beast, starting with the fact that it's really not a biopic at all. If you looked at it from just the right angle, and willfully chose to ignore the point, you could semi-accurately describe it as the story of how and why Ginsburg wrote his revolutionary work Howl and Other Poems, and the subsequent legal battle to have the sexually explicit work decreed as "not obscene", by which description I suppose it tolerably fits the generic bill. But this is not at all what the film is - it's something that I don't know that I've ever heard of before, let alone seen with my own eyes. It is an explication of the poem Howl, in fact, with each of its four separate plot threads expressing a different approach to understanding Ginsberg's work.

The first question: what are those four threads? Going chronologically, there is first Ginsberg's (James Franco) premiere of the poem in 1955 at San Francisco's Six Gallery, shown in documentarylike black and white. Then there is a 1957 interview between Ginsberg and an unseen reporter, discussing the pending obscenity trial, in grainy color. There is the trial itself, in which publisher Lawrence Ferlinghetti (Andrew Rogers) is defending Howl's value as literature, with defense attorney Jake Erlich (Jon Hamm) matching wits with prosecutor Ralph McIntosh (David Strathairn); this sequence is in "normal" color. Lastly, separate from the others, is a dramatic visual interpretation of passages from Howl, presented in highly stylised animation.

All of these strands answers, in its own way, the question of how one could appreciate the poem: as a work of biography, as a cultural object, as a key moment in the development of 20th Century American literary forms. The animated sequences take the poem's symbolism at face value, and literalise it, creating a direct cinematic analogue to Ginsberg's wandering language. This is all a fairly novel way of adapting a work of literature that is, to all appearances, stubbornly uncinematic and at best elliptically narrative. "Novel", I should point out, is by no means a necessary synonym for "successful", and Howl the movie is plagued by modest flaws, but co-directors Rob Epstein and Jeffrey Friedman have enough passion for the project, and strange and original ideas about how to execute it, to carry the whole thing across. Anyway, faced with "modestly flawed but fascinatingly unusual" versus "perfectly fine and perfectly ordinary", let no one say that I have ever come down in preference of the latter.

For a start, the movie is an absolutely ace recreation of the 1950s, one made with fairly stringent compulsion for detail (the dialogue in the trial sequences, for example, is taken essentially verbatim from court transcripts). It's not just in the design, either: the very filmic texture of the movie, courtesy of cinematographer Edward Lachman (an unjustly overlooked name considering the enviable highlights of his career, not least of which is Far from Heaven), has a marvelously convincing faux-documentary feeling - and it's not, surely, a coincidence that Epstein and Friedman are documentarians by trade, Howl being their first "narrative" film, such as it is (a previous collaboration was the excellent The Celluloid Closet; prior to Friedman's advent as a filmmaker, Epstein helmed The Times of Harvey Milk, a masterpiece of the form). Howl very much feels like the first feature of a documentary team: its approach to its subject is unusually - distractingly, even - focused on the elucidation of the facts, as opposed to the creation of a compelling dramatic arc or probing character study.

This is a singularly useful approach to the project if we agree that the purpose of Howl the movie was to contextualise and analyse Howl the poem; it does, however, leave certain parts of the movie hanging out with nowhere to go. I am chiefly thinking of James Franco: he gives quite a magnificent performance as Ginsberg that is about half impersonation, half an actor's attempt to live in the body of a man who is nervous, proud, dimly aware of his place in history, and probably high, all at the same time. The film gives him nowhere to go with this performance, unfortunately, and inevitably. Ginsberg's function in the plot is entirely due to his authorship of the book of poetry; we learn about him in dialogic terms that explains and elucidates the poem, but does not give Franco anything to play. He can only beatify. On the other hand, several of the performances in the trial sequences - which by rights ought to be even more hamstrung in this way - are actually vibrant and interesting, particularly Strathairn's: full of tiny moments, like his half-smile at one point before acknowledging that he just plain doesn't like or understand Howl. This is, perhaps, because the trial sequences are the most like a "movie" in the ordinary sense of that term.

I wonder if it's anything but my love for animation that makes me find the animated dramatisation of the poem to be the film's best element: though a bit on the nose in certain places, it's also a grand effort to yoke the poem's emotional imagery to something tangible and concrete. It helps that the animation itself is so harsh and graphic, sketchy when it needs to be, painterly when that is better. It is not particularly like any style prominent in the 1950s, which if anything just furthers the film's argument that Howl was a revolution, years-ahead-of-its-time work, for the now as much as it is of its moment.

And here we come to perhaps the single biggest problem with the film: it is hagiographic. Not towards a person (though Ginsberg comes across as rather saintly), but towards Howl itself. Full disclosure: I've never read the poem. But quite a lot of it is read aloud in the film, and to be perfectly honest, I do not know that the film makes the argument that it's quite the towering masterpiece that it has to be for the film to wholly justify itself. For every stunning image or turn of phrase, there's another that sounds like a young man desperately trying and not quite succeeding in nailing his thoughts down on paper. And in all of its four threads, the film Howl inadvertently succeeds in reinforcing that idea: Ginsberg was a sensitive, callow youth, who tapped into a Zeitgeist that was not entirely based on rewarding merit so much as attitude. Honestly, the film seems as much a celebration of half-formed maturity as much as anything, which can hardly have been the point.

That said, it serves as a fairly exhaustive, involving tribute to one of the seminal post-WWII literary achievements. I hate to end up writing it off with the pithy dismissal, "especially good for fans of the poem", but I guess I must. And since the filmmakers are obviously fans of the poem, I consider that Howl is exactly what it set out to be, and thus can only be regarded as a success.