Beloved fantasy author Terry Pratchett has died at the age of 66, according to a message from his publishers. Best known for the Discworld novels, Pratchett wrote more than 70 books, blending fantasy elements with cutting and humane satire. "The world has lost one of its brightest, sharpest minds," said Larry Finlay, who worked with Pratchett at Finlay Publishers. "My sympathies go out to Terry's wife Lyn, their daughter Rhianna, to his close friend Rob Wilkins, and to all closest to him."

Pratchett's family made the announcement through a series of tweets on the author's official Twitter account. The tweets describe an encounter between Pratchett and the personification of Death, who was a frequent and beloved character in the Discworld novels.

AT LAST, SIR TERRY, WE MUST WALK TOGETHER. — Terry Pratchett (@terryandrob) March 12, 2015

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

Pratchett was diagnosed with an aggressive form of Alzheimer's Disease in 2007, which left him mentally diminished but still able to write. He continued to work — publishing the 40th Discworld novel in March of last year — and published numerous essays about his struggles with disease. "Dementia attacks those facets which make us who we are, and it’s a deeply personal attack that defies prediction," he wrote in one recent piece. "There isn’t one kind of dementia. There aren’t a dozen kinds." In July, he was forced to cancel a reading in the face of worsening symptoms, telling fans, "the Embuggerance is finally catching up with me."

Pratchett's family has set up a page for donations in Pratchett's memory, raising funds for the Research Institute to the Care of Older People.