Fantasy author Sir Terry Pratchett has died aged 66, having had Alzheimer's disease for eight years.
Best known for the Discworld series, Sir Terry wrote more than 70 books over his lengthy career.
He was first diagnosed with Alzheimer's in 2007, but continued writing, completing his final book last summer.
"The world has lost one of its brightest, sharpest minds," said Larry Finlay of his publishing company, Transworld.
In over 70 books, Terry enriched the planet like few before him," he added.
"As all who read him know, Discworld was his vehicle to satirize this world: He did so brilliantly, with great skill, enormous humour and constant invention.
"Terry faced his Alzheimer's disease (an 'embuggerance', as he called it) publicly and bravely. Over the last few years, it was his writing that sustained him. His legacy will endure for decades to come.
The Discworld series - which started in 1983 - was based in a flat world "perched on a tortoise's back". By 2013, he had written more than 40 instalments.
At the peak of his writing powers, Sir Terry was publishing more than three books a year. His quirky and satirical view of the world won him a worldwide following.
At the turn of the century, he was Britain's second most-read author, beaten only by JK Rowling.
Known for his striking dress sense and large black fedora, Sir Terry was awarded an OBE for services to literature in 1998.
In August, 2007, it was reported he had suffered a stroke, but the following December he announced that he had been diagnosed with a very rare form of early-onset Alzheimer's disease which, he said, "lay behind this year's phantom stroke".
With typical Pratchett humour, the author's official Twitter account posted a last tweet.
The End.— Terry Pratchett (@terryandrob) March 12, 2015
The author died at home "with his cat sleeping on his bed, surrounded by his family," his publisher Larry Finlay said.
"My sympathies go out to Terry's wife Lyn, their daughter Rhianna, to his close friend Rob Wilkins, and to all closest to him."