Colleen McCullough, the Australian author best known for the international bestseller The Thorn Birds has died, after what reports are referring to as “a long illness.” She was 77.

Born in New South Wales and trained in neuroscience, McCullough went on to pen 24 books, including a seven-volume sequence of novels set in ancient Rome and a biography of Australian soldier and diplomat Roden Cutler. Her 1974 novel Tim, about the relationship between a mentally challenged handyman and the middle-aged woman who hires him, was made into a movie starring Mel Gibson and Piper Laurie.

But it is The Thorn Birds for which McCullough will be most widely remembered. Published in 1973, the novel has sold more than 30 million copies worldwide, and was made into a television miniseries starring Richard Chamberlain, Barbara Stanwyck, and Christopher Plummer. First broadcast on ABC in 1983, the miniseries won six Emmys and four Golden Globes.

Though best known as a novelist, McCullough came to writing relatively late, having studied neurophysiology at Sydney University. From The Australian:

After graduation she set up the department of neurophysiology at Sydney’s Royal North Shore Hospital and ran this department for five years. In quest of a higher degree, she left for London. She studied and worked at the Hospital for Sick Children in Great Ormond Street (associated with London University) and at a neurology unit in Birmingham….

McCullough’s scientific work was considered to be outstanding and she was invited to move to the U.S. to run an expanding research laboratory in the medical school at Yale University. Here she taught neuroanatomy, neurophysiology and neurological electronics. She also worked on microsurgical techniques. She remained at this university for 10 years and spent 14 years in all in America.

Elsewhere, The Australian quotes Prime Minister Tony Abbott as saying that McCullough was a “unique … personality” and that her Cutler biography “will always be required reading for those who want to know the story of one of Australia’s great heroes and NSW’s longest serving governor.”

McCullough’s last novel, poignantly titled Bittersweet, appeared in 2013.