Cramer grew up in Seattle, and currently lives in Pleasantville, New York with her husband David G. Hartwell and their two children. She is the daughter of physicist John G. Cramer. She is a graduate of Columbia University, with degrees in mathematics and American studies.

Cramer has worked for five literary agencies, most notably the Virginia Kidd Agency, and for several software companies, Hypertext Horizon: An Interview With Kathryn Cramer including consulting with Wolfram Research in the Scientific Information Group. She co-founded The New York Review of Science Fiction in 1988 and was its co-editor until 1991 and again since 1996. It has been nominated (as of 2007) for the Hugo Award for Best Semiprozine every year of its existence, fifteen times under her co-editorship.

Cramer was the hypertext fiction editor at Eastgate Systems in the early 1990s. She was part of the Global Connection Project, a joint project of Carnegie Mellon University, NASA, Google, and National Geographic using Google Earth and other tools following the 2005 Pakistan earthquake.

Anthologies

• The Architecture of Fear (1987) with Peter D. Pautz — winner of the World Fantasy Award for Best Anthology
• Spirits of Christmas (1989) with David G. Hartwell, Tor Fantasy, ISBN 0-81255-159-1
• Walls of Fear (1990), Avon Books, ISBN 0-38070-789-6 — a World Fantasy Award nominee
• The Evolution of Hard SF (1994) with David G. Hartwell, ISBN 0-312-85509-5
• The Hard SF Renaissance (2002) with David G. Hartwell, Orb books, ISBN 0-31287-636-X
• The Space Opera Renaissance (2006) with David G. Hartwell, Tor Books, ISBN 0-76530-617-4
• Masterpieces of Fantasy and Enchantment (1988) with David G. Hartwell
• Masterpieces of Fantasy and Wonder (1994) with David G. Hartwell

Anthology Series

• Year’s Best Fantasy 1 through 7 (2001—2007) with David G. Hartwell (HarperCollins 2001—2005, Tachyon Publications 2006—2007)
• Year's Best SF 7, Year's Best SF 8, Year's Best SF 9, Year's Best SF 10, Year's Best SF 11, Year's Best SF 12, Year's Best SF 13, Year's Best SF 14 (2002—2009) with David G. Hartwell (HarperCollins)

Short Fiction

• "Forbidden Knowledge" in Mathenauts, MathFiction: Mathenauts: Tales of Mathematical Wonder (Rudy Rucker (editor)) ed. Rudy Rucker (1987)
• "The End of Everything" in Asimov's Science Fiction October 1990
• In Small & Large Pieces by Kathryn Cramer, in The Eastgate Quarterly Review of Hypertext, Volume 1, No. 3, Eastgate Systems (1994). (a work of hypertext dark fantasy)
• " Disextinction" in Nature Magazine (2001)
• " Sandcastles: a Dystopia" in Nature Magazine (2005)

Essays

• How Shit Became Shinola: Definition and Redefinition of Space Opera with David G. Hartwell, SFRevu August 2003

Cramer has also written a number of essays published in the New York Review of Science Fiction. She is a contributor to the Encarta article on science fiction and wrote the chapter on hard science fiction for the Cambridge Companion to Science Fiction ed. Farah Mendlesohn & Edward James. Several of her essays have been reprinted, for example "Science Fiction and the Adventures of the Spherical Cow" (NYRSF August 1988) in Visions of Wonder, ed. Milton T. Wolf & David G. Hartwell (Tor 1996).