He was educated at the Royal High School of Edinburgh and Downing College, Cambridge, where he studied English; he was a Cambridge Apostle. He became literary editor of The Spectator and the New Statesman. Miller resigned from the latter over a disagreement with the magazine's then editor Paul Johnson, over the extent to which the literary pages treated difficult subjects and also Johnson's disapproval of The Beatles and their fans.
He was then editor of The Listener (1967–73) and subsequently the London Review of Books, which he founded, from 1979 to 1992. He was also Lord Northcliffe Professor of Modern English Literature and head of the English Department at University College, London until 1992.
- Poetry from Cambridge 1952–4. Oxford, 1955 (editor)
- Writing in England today: the last fifteen years. London: Penguin, 1968 (editor)
- Memoirs of a Modern Scotland. London: Faber, 1970 (editor)
- Cockburn's Millennium. London: Duckworth, 1975 (a biography of Henry Cockburn, Lord Cockburn, which won Miller the James Tait Black Memorial Prize)
- Doubles: studies in literary history. Oxford: Oxford University Press, 1985 (criticism)
- Authors. Oxford: Clarendon, 1989
- Rebecca's Vest: a memoir. London: Hamish Hamilton, 1993
- Boswell and Hyde. London: Syrens, 1995
- Dark Horses: an experience of literary journalism. London: Picador, 1998 (memoir)
- Seamus Heaney in conversation with Karl Miller. London: BTL, 2000
- Electric Shepherd: A Likeness of James Hogg. London: Faber, 2003 (biography)
- Tretower to Clyro: essays. London: Quercus, 2011
- "Weekend birthdays". The Guardian (Guardian Media). 2 Aug 2014. p. 51.
- Neil Berry (2002) Articles of Faith: The Story of British Intellectual Journalism, London: The Waywiser Press, p.214 ISBN 1-904130-08-9.
- "Karl Miller, founding editor of London Review of Books, dies at 83". The Guardian. 25 September 2014.
- Sutherland, John (25 September 2014). "Karl Miller obituary". The Guardian.