His father was the biologist Joachim Illies, and one of his school teachers was the writer Gudrun Pausewang.

He worked as culture editor for major German newspapers such as Frankfurter Allgemeine Zeitung and Die Zeit.

In 2004, he cofounded the contemporary art magazine monopol with his wife Amélie von Heydebreck.

In January 2019, he joined the Rowohlt Verlag publishing house as a managing director.

[1] Illies' biography about Caspar David Friedrich, The Magic of Silence, was published in 2023.