ALONG time in the imagination, and several years in the making, Gray's Fleck began as an attempt at "an imitation – not a translation!" of Goethe's Faust, a radio production read by Louis MacNeice having so compelled his myth-guzzling 14-year-old self. He found Goethe's final addition to Faust a "rotten ending for the play", and "wanted to wrench the story into (his] own vision of the 20th and 21st century", so we find in Fleck an odd hybrid thing written in modern verse, the more strange for being Gray's visual rendering.

Fleck, a "muddled soul. A mammy's boy. A teacher's pet", is the Job-like pawn in a wager between God and Nick, part Mephistopheles, part Miltonic Satan. The vision of Fleck, bored, lonely and frustrated that his life's work has come to no good, and the scene with the spirit which unfolds thereafter, are loyal to the first act of Faust, but Gray adds his own flourishes and deviates completely in the other acts. Fleck, for instance, can be Hamlet one moment – dramatically caressing a skull, bemoaning his failure in the light of the Milky Way; and Sandy from Grease the next – his montage from fatty to fitty complete with beauticians and a mirror ball.

These, and other mad quirks of Gray's mind, resonate with the much wilder imaginings of Lanark's Unthank. But Fleck is a disappointingly unprepossessing figure; even with the complete picture, that he is being used "to annoy someone" that Nick hates, he is meekly led. There is none of the crazed thirst for power in him, as found, for instance, in the Faust of Carol Ann Duffy's entertaining Mrs Faust: he is plucky, bastardly, "didn't have a soul to sell", which contextualises his greedy collusion. Fleck, however, has a "wretched little soul" that is only made stultified and content by marriage and baby, steadfastly using his new power for his own worthy means.

It is Nick who is the antihero of the piece. Charming, annoying, with a range of voices and accents, as self-titled "jester of the universe" everything pivots around him. He masterminds a trip to a casino in which drug dealers and nude mud wrestling lurk, and a media junket of Pee, Cue and Kay, who provide a humorous insight into the political spectrum of the media. Nick match-makes and saves face, all in an attempt to win Fleck round to the side of evil. Fleck's flaky character is more markedly a dramatic pity, cast under Nick's shadow as he is.

Gray's adherence to the age-old face-off between Nick and that "dog-spelled backwards", the tug-o-war between good and evil and the exploration of "how much creative energy has an evil source", is interestingly handled. Gray's "God the Dad" is "seldom convincingly described as good and loving", and isn't here either. He goads Nick to do his wicked best. God is all at once a "squirt of piss!" a "stinking sod!", a gun-supplying literal deus ex machina and a normal guy who, in a fabulously detailed Gray stage direction, "has the local accent of a working-class man who, through a university education, has an important professional job".

And Gray's representation of God sums up what makes this, another in a long list of Faust-inspired texts, worth a look. Gray's wry irreverence is in full and pungent flow. With a torture scene involving an episode of The Simpsons and a speech interrupted by mobile phones, he achieves what he wants to by dragging Faust into the 21st century. It has lights and music and molls and liquor and, though it verges on the brassy cabaret side of things, in turning Faust the tragedy into Fleck the comedy, he succeeds in paying his own delirious, wholly un-Goethean tribute.

With manikins cast in the peripheral roles and a closing couplet of "I hope our entertainment pleased you well/ – it has no moral. See you all in hell!" it offers a palate of dark and light Gray at once. Thus, while perhaps merely an insubstantial 'brain fart' in the grand scheme of Gray's oeuvre, it's an entertaining and not unwelcome one.