Over a whopping two hours and 20 minutes, film-maker Edgar Wright consummates a gigantic act of fanboy love for the glam art-pop duo Sparks, who hailed from California but found fame in Britain on Top of the Pops in the 1970s. Fronted by brothers Ron and Russell Mael, Sparks have continued recording and touring through good times and bad while amassing a fanatical following. Ron is the deadpan one at the piano with the Chaplin/Hitler moustache, and Russell the more extravagant and dishy lead singer.

The film has to be this long because Wright basically wants to take us through their career on an uncompromising, record-by-record basis, and they have put out 25 studio albums.It is simultaneously exasperating and magnificent that he shows no interest whatever in asking the Mael brothers anything about their personal, emotional or romantic lives. Actually, they are probably closer than a married couple; each is the other’s emotional life, although this too is finally opaque. Wright asks how they can be so adored, so influential in many ways, and yet still unknown – and his film just has to be content with not knowing the answer to this either.

I have to admit that I really knew little or nothing about Sparks before this, and for a long time I actually thought they were British, basically because Ron’s purse-lipped eye-rolling and grimacing at the camera reminded me of Kenneth Williams or Blakey from On the Buses. But Wright’s film has converted me. Sparks are the Gilbert and George of pop music. Or maybe it’s truer to say Ron and Russell are the continuing reincarnation of Pete’n’Dud; they are funny, perhaps uniquely so in genuinely fusing pop music and humour, in their extraordinary, surreal lyrics and brilliant album designs.

There is a funny anecdote from Nick Heyward from Haircut One Hundred, who says that as a kid he saw them in the street and was so scared he wanted to hide. In the past, the Mael brothers had abortive film projects with Jacques Tati and Tim Burton, but have now found success with their operatically crazy movie Annette, directed by Leos Carax. They are having a moment, but perhaps their genius resides in having had one long continuous moment from 1971 to the present day.

• The Sparks Brothers is released on 29 July in cinemas.