The writer and artist Alasdair Gray, who blazed a trail for contemporary Scottish fiction with his experimental novels, has died aged 85.

Gray’s publisher Canongate announced the news on Sunday, saying he died early in the morning after being hospitalised for a short illness in his home city of Glasgow. In a statement, Gray’s family thanked his friends and hospital staff, calling him “an extraordinary person; very talented and, even more importantly, very humane”.

Among those to pay tribute were author Val McDermid, who credited Gray for having “transformed our expectations of what Scottish literature could be”, and Scotland’s first minister Nicola Sturgeon, who called him “one of Scotland’s literary giants, and a decent, principled human being.” “He’ll be remembered best for the masterpiece that is Lanark, but everything he wrote reflected his brilliance,” she added on Twitter. “Today, we mourn the loss of a genius, and think of his family.”

The novelist Ali Smith called Gray “a modern-day William Blake” and said: “He was an artist in every form. He was a renaissance man. His generosity and brilliance in person – felt by everyone who knew him even a little – were a source of astonishing and liberating warmth. The few times I met him in life, he was all these things in a unique combination of polite, frank, detached (or maybe more truly differently attached), sanguine, many-voiced, wise, warm, kind, hilarious, acutely truth-telling, uncompromisingly articulate.”

Gray came to fiction late, publishing his first novel Lanark at the age of 46 in 1981. A experimental, pornographic fantasy – 1982, Janine – followed three years later, with his rambunctious reworking of Mary Shelley’s Frankenstein, Poor Things, appearing in 1992. As his literary reputation increased, winning both the Guardian fiction prize and the Whitbread novel award in 1992, the elaborate illustrations he created for his books began to draw attention to the pictorial art Gray had been producing all along. The stream of commissions for murals and portraits gradually increased, and he finished his career as one of Scotland’s most admired and versatile artists.

Born in the northeast of Glasgow in 1934, Gray was brought up on an estate the writer once described as “one of the earliest and most posh of the municipal housing schemes”, remembering the schoolteachers, printers and local civil servants who lived in his close. He studied painting at the Glasgow School of Art, and worked as a muralist, part-time art teacher and theatrical scene painter while writing scripts for TV and radio.

In 1954, Gray began writing the novel that would occupy him on and off throughout the 1960s and 70s. Lanark divides the story of a life into four books, alternating between Glasgow and a shadowy version of the city called Unthank. The novel opens with book three, in which a young man finds himself in a dark metropolis filled with strange diseases, and then jumps back to fill in the story of Duncan Thaw, who grows up in Glasgow just before the second world war. The Guardian called it “fluent, imaginative”, a novel “of undeniable quality, but rare, and not for all tastes, like an oyster, or a truffle”.

This truffle was soon compared to Joyce’s Ulysses, and was the making both of the author and his independent publisher, Canongate. Writing 20 years later, Janice Galloway remembered how the novel’s “exuberant, at times despairing, always vivid voice” made her feel “acknowledged, spoken to, listened for”. As Thaw suggests in the novel, Glasgow’s magnificence had remained unnoticed, because “if a city hasn’t been used by an artist, not even the inhabitants live there imaginatively”. Writers such as Galloway, Ian Rankin, Irvine Welsh and Ali Smith woke up to find their own world given back to them in fiction, and Scotland’s cultural confidence enlarged.

Gray followed it with 1982, Janine – an intricate sadomasochistic fantasy so typographically complex that the author insisted his contract contained provision for up to six rounds of proofs – before turning to a more conventional realism for three novels exploring nationalism and power. Poor Things, a patchwork of Victorian fragments, returned to tricksier territory, charting Bella Baxter’s rise from the creation of gifted surgeon Godwin Bysshe Baxter to become her own woman. The Guardian hailed it as “a bibliophile’s paradise of postmodern precision” and awarded Gray its 1992 fiction prize.

As his public profile began to rise, Gray began to publicly support Scottish independence, publishing a short polemic called Why Scots Should Rule Scotland in time for the 1992 election. Devolution was never enough for the author, who agreed with Margaret Thatcher when she claimed Tony Blair as her greatest achievement. “Like US citizens,” Gray argued, “the UK electorate has no chance of voting for a party that will do anything to seriously tax our enlarged millionaire class that controls Westminster.”

The steady stream of novels, short stories and non-fiction continued, including an illustrated translation of Dante’s Inferno published in 2018. But alongside his writing, Gray carried on painting. Speaking to the Guardian in 2010 as he published a survey of his visual art, the author explained that since his parents had given him crayons and paper even before he could read, painting was perhaps more natural than writing, but “one is always a tremendous holiday from the other”.

Detail from Alasdair Gray’s 1977 Marion Oag and the Birth of the Northern Venus Photograph: © The artist (and Sorcha Dallas, Glasgow)/Arts Council Collection

“I feel healthier painting than writing,” he said, “because when you’ve been writing a lot and your head is full of words, you are still muscularly not exhausted, but you’re nervously exhausted, so in order to sleep you go out and drink heavily, unless you’re more disciplined than I am.”

Gray confessed himself sometimes rather surprised by his own productiveness, despite what he called “my alcoholism”, reflecting ruefully on how his life might have been changed if he had found financial success a little earlier in his career. “I think I would have painted much more than I did,” he said.