Press Association via AP Images
Isabella Biedenharn
March 12, 2015 AT 04:11 PM EDT

Sir Terry Pratchett, author of the popular Discworld comic series, has died. He was 66.

Pratchett’s Twitter account, which he shares with Rob Wilkins, has published some poignant tweets about the news:

Pratchett suffered from Alzheimer’s disease (calling it an “embuggerance”) and PCA but continued to write. Pratchett wrote over 70 books throughout his lifetime, and the Discworld universe has spawned board games, music, popular science books and many other companion publications. His last Discworld book was completed in the summer of 2014.

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