Author Terry Pratchett has died at the age of 66 after a battle with Alzheimer's.

The bestselling and much-loved author writer died at home on Thursday, surrounded by his family and with his cat sleeping on his bed, according to a statement which is published in full below.

Pratchett's Facebook page was updated to say: "It is with immeasurable sadness that we announce that author Sir Terry Pratchett has died.

"The world has lost one of its brightest, sharpest minds. Rest in peace Sir Terry Pratchett."

The Discworld writer's death was announced on his Twitter profile.

Terry took Death’s arm and followed him through the doors and on to the black desert under the endless night. Terry Pratchett (@terryandrob) March 12, 2015

The End. Terry Pratchett (@terryandrob) March 12, 2015

He publicly suffered with posterior cortical atrophy, a variation of Alzheimer's, which he was diagnosed with in 2007.

Pratchett wrote over 70 books, including 40 as part of the fantasy Discworld series, and sold over 85 million copies in his lifetime.

As soon as news broke of his death broke on Thursday afternoon, his website crashed under the weight of fans wanting to remember the writer.

Terry Pratchett: A career in quotes Show all 13 1 /13 Terry Pratchett: A career in quotes Terry Pratchett: A career in quotes “Inside every sane person there’s a madman struggling to get out” –The Light Fantastic Pratchett photographed in 1990 Corbis Terry Pratchett: A career in quotes "We Pratchetts are a feisty bunch" Pratchett with his daughter Rhianna at home in 2009. Rhianna is now a writer in her own right and has written the storylines to video games such as Tomb Raider and Overlord Rex Features Terry Pratchett: A career in quotes "It occurred to me that at one point it was like I had two diseases - one was Alzheimer's, and the other was knowing I had Alzheimer's" Terry Pratchett delivers a petition on behalf of the Alzheimer's Research Trust calling for an increase in government funding for dementia research in 2008 Getty Images Terry Pratchett: A career in quotes "Imagination, not intelligence, made us human" Terry Pratchett with his double-row of six computer screens in 2009 George Wright Terry Pratchett: A career in quotes “If you don’t turn your life into a story, you just become a part of someone else’s story” Pratchett was awarded an OBE in 1998 PA Terry Pratchett: A career in quotes “Sometimes glass glitters more than diamonds because it has more to prove” - The Truth Terry Pratchett launches his 25th novel of the 'Discworld' series, 'The Truth' in 2000 Corbis Terry Pratchett: A career in quotes “Time is a drug. Too much of it kills you” In 2007, the year he announced he had Alzeihmer's Getty Images Terry Pratchett: A career in quotes "You can't ask a fantasy writer not to want a knighthood" Receiving his knighthood in 2009 AFP PHOTO/Ian Nicholson/POOL Terry Pratchett: A career in quotes "Life doesn't happen in chapters - at least, not regular ones" Pratchett at home in 2009 Rex Terry Pratchett: A career in quotes “The trouble with having an open mind, of course, is that people will insist on coming along and trying to put things in it” Pratchett at the world congress of the World Federation of the Right-to-Die Societies in Zurich, 2012 Corbis Terry Pratchett: A career in quotes “Inside every sane person there’s a madman struggling to get out” Attends the South Bank Sky Arts Awards in 2012 Getty Images Terry Pratchett: A career in quotes "Insanity is Catching" Pratchett won the Bollinger Everyman Wodehouse Prize at the Telegraph Hay Festival, pictured with Snuff the pig in 2013 Getty Terry Pratchett: A career in quotes “People don't alter history any more than birds alter the sky, they just make brief patterns in it” - Mort Campaigning for Dementia Friends in 2014 PA

He is survived by his wife Lyn and their daughter Rhianna, who retweeted the messages posted on Pratchett's Twitter feed.

A JustGiving page has been set up in his name, which aims to raise money for the Research Institute for the Care of Older People.

Pratchett was also an outspoken supporter of assisted dying. "Rather than let Alzheimer's take me, I would take it," he said in 2010. "I would live my life as ever to the full and die, before the disease mounted its last attack, in my own home, in a chair on the lawn, with a brandy in my hand to wash down whatever modern version of the 'Brompton cocktail' some helpful medic could supply.

"And with Thomas Tallis on my iPod, I would shake hands with Death."

Terry Pratchett supported the Dementia Friends campaign (PA)

Last summer, Pratchett was forced to cancel an appearance at The International Discworld Convention, as his Alzheimer's - which he called "the embuggerance" - was "catching up" with him.

Pratchett was knighted in 2010, when he decided to forge his own sword out of meteorite.

A full statement reads as follows:

It is with immeasurable sadness that we announce that author Sir Terry Pratchett has died at the age of 66.

Larry Finlay, MD at Transworld Publishers: "I was deeply saddened to learn that Sir Terry Pratchett has died. The world has lost one of its brightest, sharpest minds.

In over 70 books, Terry enriched the planet like few before him. 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.

My sympathies go out to Terry's wife Lyn, their daughter Rhianna, to his close friend Rob Wilkins, and to all closest to him."

Terry passed away in his home, with his cat sleeping on his bed surrounded by his family on 12th March 2015. Diagnosed with PCA [posterior cortical atrophy] in 2007, he battled the progressive disease with his trademark determination and creativity, and continued to write. He completed his last book, a new Discworld novel, in the summer of 2014, before succumbing to the final stages of the disease.