 Gillen has worked for publications such as "PC Gamer UK", "The Escapist", "Amiga Power" (under the pseudonym "C-Monster"), "Wired", "The Guardian", "Edge", "Games Developer", "Develop", "MCV", "GamesMaster" and "PC Format", among others.On the web, Gillen was a founder of and major contributor to the PC gaming site "Rock, Paper, Shotgun" and a games reviewer for "Eurogamer".He is notable for his manifesto for New Games Journalism, more simply the model of New Journalism applied to video game journalism.