In 1998, George Michael was arrested for public lewdness in an LA lavatory, an incident that finally led the singer to publicly come out. The following day, Sathnam Sanghera found himself unable to leave his room at university: the doorway had been mockingly plastered with tabloid newspaper headlines – “ZIP ME UP BEFORE YOU GO-GO!” – by fellow students aware of his longstanding fandom. As a writer, Sanghera is best known for a series of award-winning books on the British empire, which he calls his “specialist subject”. Judging by Tonight the Music Seems So Loud – not a biography so much as a miscellany, a set of themed essays that tend to digress in all kinds of intriguing directions – the life and work of one Georgios Panayiotou runs imperialism and its legacy a very close second.

It is an unashamedly partisan book, although not an uncritical one. Sanghera is as alive to Michael’s personal and professional failings (whether the naffness of some of his early work as one half of Wham! or his high-handed treatment of the duo’s other half, Andrew Ridgeley) as he is in love with his artistic triumphs. These, of course, range from Careless Whisper and Wham!’s annually inescapable Last Christmas to the 1996 solo masterpiece Older, a peculiar and peculiarly effective cocktail of raw grief at the Aids-related death of his lover Anselmo Feleppa and unrepentant horniness.

Sanghera’s love for his subject is evidently sharpened by the opprobrium of others. Indeed if the book has a flaw, it’s that the author is old enough to remember an era when George Michael was deemed insufferably uncool by some arbiters of taste (incredibly, when Wham! performed at a 1984 benefit show for striking miners, the only mainstream pop act to show support for the cause, they were received stone-faced by the audience and savaged by the music press for their trouble), and thus has a tendency to underestimate how much both he and his music have been critically re-evaluated in the 21st century.

He says one of the spurs to write the book was his belief that “most truly popular music is not generally deemed worthy of serious analysis and George Michael’s music most certainly is not”. That might have been true once, but certainly not of late: when he died, this newspaper alone ran six features by critics analysing different aspects of his music. “He sang so exquisitely about the marrow of life, about the vital, corporeal things”, wrote one, which definitely doesn’t amount to taking George Michael insufficiently seriously.

But if Sanghera occasionally seems like a man doughtily fighting a battle that’s already won, it doesn’t really impede his narrative, which traces Michael’s progress from pudgy, acne-ridden teen, to pop star girls screamed at, to gay icon, and is packed with anecdotes, sharp analysis and context. Sanghera is very good on the climate of homophobia in the 80s, which might have given any gay public figure serious qualms about coming out, and fascinating on Michael’s family background: how growing up embedded in north London’s Greek Cypriot community impacted on everything from Wham!’s image – not camp, Sanghera suggests, but “the vision of two children of immigrants imagining a kind of glamour they had not actually experienced before” – to his work ethic and control freakery. His dad made good in England by working exceptionally hard, running such a tight ship at his restaurant that he summarily fired his only son for messing up the drinks orders. The fact that the same son went on to hire 12 different saxophonists before finding one that could play the solo on Careless Whisper to his satisfaction doesn’t come as a huge surprise.

This my-way-or-the-highway perfectionism could yield hugely impressive results – Careless Whisper’s sax hook may well be the most famous in pop history – but it could equally lead to intransigence and self-sabotage. Michael worked incredibly hard to transform himself from a member of a teen pop band into a more adult-facing solo artist, but having sold a staggering 25m copies of his 1987 solo debut Faith, he refused to promote its follow-up Listen Without Prejudice Vol. 1, or even make videos for its singles: a better album than its predecessor, it achieved only a fraction of its sales as a result. It was evidence of a deeply contradictory nature that occasionally has Sanghera throwing up his hands in bewilderment.

Michael was a polymath, keen to be duly credited as the sole singer, writer, producer and musician on a succession of tracks, but also had a weird habit of talking down his abilities, claiming he couldn’t play instruments he was perfectly capable of playing. He was a Stakhanovite who increasingly worked at an agonisingly glacial pace, endlessly fussing over details, a state of affairs not much helped by his gargantuan appetite for marijuana: coupled with bouts of writers’ block, it meant he released only six albums of original material in a career that lasted 34 years. He was a Labour voter, booster of the NHS and famously generous philanthropist who also engaged in tax avoidance. After being publicly outed, he became a notoriously frank interviewee (“as if nothing can embarrass him anymore” the Guardian’s Simon Hattenstone suggested when he met him in 2009). But even as he skinned up in front of journalists and freely discussed his drug use and sex life, he was concealing the extent of the addictions that eventually killed him.

Michael emerges as a messy, unpredictable but ultimately hugely likable figure, which makes the essay about his demise particularly tough reading. Listed starkly on the page, the facts of his final 10 years make it obvious that he was a deeply unwell man whose life had spun wildly out of control: drug busts, medical emergencies, visits to rehab, rumours of breakdowns and suicide bids and seven incidents in which he either crashed his car or was found comatose at the wheel.

That it somehow didn’t appear obvious at the time – that his death at 53 felt like a shock rather than a grim inevitability – seems remarkable, but as Sanghera points out, Michael’s professionalism did a lot to paper over the cracks. He was always available to the media and always smart, funny and self-effacing: to use a modern turn of phrase, he controlled the narrative. He was punctilious about his appearance – the star certainly never looked like an ailing drug addict – and unfailingly superb onstage.

Behind the scenes, it was a different story. He struggled to make new music: at one juncture he booked six months of recording sessions but never turned up to the studio once. His once-acute commercial instincts seemed to desert him: even Sanghera can’t muster much enthusiasm for the handful of still-unreleased songs he completed in his final years. He cut off close friends and family who tried to intervene. No one who knew him seems to have been particularly surprised by his death: the list of adjectives used to describe him on his official website now includes not just “icon” “legend” “soul singer” and “philanthropist” but “addict” “repeat offender” and “depressive”.

As the book draws to a close, Sanghera offers a heartbreaking alternative history. He imagines Michael conquering his addictions, coming to a complete accommodation with his musical past (to the end of his life, he was dismissive of Wham!, describing their oeuvre as an exercise in “ignoring my own intelligence” and declining to play most of their hits live) and headlining Glastonbury, “getting pleasure from the audience reaction to Club Tropicana”.

It’s affecting because you can imagine it so vividly: the endless succession of hits that anyone with even a passing interest in pop music knows, the pandemonium in the crowd when he breaks out Careless Whisper, the encore of Freedom ’90. You don’t have to be a fan on Sanghera’s level to understand what a triumph it would have been.