(CNN)Best-selling British espionage writer David Cornwell -- known to the world as John le Carré -- died Saturday at 89, according to his literary agent.
Le Carré's family said in a statement that he died from pneumonia. He is survived by his wife, Jane, and four sons.
"I represented David for almost 15 years. I have lost a mentor, an inspiration and most importantly, a friend," said Jonny Geller, CEO of literary agency The Curtis Brown Group. "We will not see his like again."
Described by Geller as the "undisputed Giant of English literature," le Carré wrote 26 books that have been published in over 50 countries and 40 languages, according to his official website.
Le Carré was born in 1931 and attended the universities of Bern and Oxford. He also served briefly in British Intelligence during the Cold War.
His most famous works spanned some six decades and included "The Spy Who Came In Form the Cold," which was published in 1963 and made le Carré "the most famous spy writer in the world," Geller said.
Le Carré also wrote "Tinker Tailor Soldier Spy" and "A Most Wanted Man," which were made into blockbuster movies.
Authors took to social media to mourn le Carré.
"This terrible year has claimed a literary giant and a humanitarian spirit," Stephen King tweeted.
British historian and author Simon Sebag Montefiore tweeted he was "heartbroken" over le Carré's death, calling him a "titan of English literature" who was up with the greats.
British actor and writer Stephen Fry tweeted he was unable to name a contemporary writer who has given him more "richer pleasure" than le Carré.
"I suppose the best one can do to honour his great life & talent is go back to 'Call For The Dead' and reread all his books," Fry wrote. "The very opposite of a chore."