Lin-Manuel Miranda gives us an unashamed sugar rush of showbiz rapture and showbiz solemnity in this heartfelt tribute to Broadway talent Jonathan Larson, played here by Andrew Garfield. Larson was the composer who created the smash-hit 90s show Rent but died at 35 of an aortic failure, just before opening night, an almost unbearable metaphor for the backstage heartbreak of musical theatre. (Miranda himself has a cameo as a short-order cook in the diner where Larson had to work as a waiter in his early years.)

This movie has been adapted by screenwriter Steven Levenson from tick, tick … BOOM!, Larson’s autobiographical piece that came just before Rent, and told the story of his first major musical project: a wildly ambitious futurist fantasy called Superbia that almost no one seemed to get. The film is about an irony that was to afflict Larson in ways he couldn’t have conceived: the ordeal of the quarter-life crisis, the first glimmers of approaching mortality and the realisation that options are closing down, something that particularly afflicts those approaching their 30s in the creative arts who don’t seem to be making it. When do you cut your losses and bail out for a straight, boring job in, say, advertising? The world is ticking like a time bomb and soon your career will blow up, and not in a good way.

But Larson has someone who believes in him: Stephen Sondheim (played in cameo by Bradley Whitford) who gives him gentle advice, crucially about the lack of a decent song to close act two of Superbia, a song which will encapsulate the all-important concept of choice. Larson has a block about writing this song, because of his commitment issues with girlfriend Susan (Alexandra Shipp).

Garfield is good at portraying the needy, borderline-desperate world of the theatrical writer: always charming, always on, always looking for creative inspiration, always on the verge of exhaustion, and now trying to absorb the new possibility of disillusion. It is a rather Sondheimian theme and Larson himself was a devotedly Sondheimian composer. This is not a movie which gives its hero a happy ending: there is no opening night for Larson, just a belief that the unending slog will one day be worth it.

• tick, tick … BOOM! is released on 12 November in cinemas, and on 19 November on Netflix.