• An Unofficial Companion to the Novels of Terry Pratchett, Westport, Ct. and Oxford: Greenwood Press, 2007.
• Christopher Priest: The Interaction, London: Science Fiction Foundation, 2005.

With Mark Bould, Adam Roberts and Sherryl Vint

• Fifty Key Figures in Science Fiction, London: Routledge, 2010.
• The Routledge Companion to Science Fiction, London: Routledge, 2009.

With Edward James and Farah Mendlesohn

• Terry Pratchett: Guilty of Literature, Baltimore, Maryland: Old Earth Books, 2004, second edition.
• Terry Pratchett: Guilty of Literature, Reading: Science Fiction Foundation, 2000. (Nominated for Hugo Award.)

With Farah Mendlesohn

• The True Knowledge of Ken MacLeod, Reading: Science Fiction Foundation, 2003.

With Andy Sawyer and Farah Mendlesohn

• A Celebration of British Science Fiction, Guildford: Science Fiction Foundation, 2005.