 Firrell's body of work includes investigations into portraiture (Text Portrait of Howard Jacobson, Booker Prize winner, 2010) and explorations of the power of mass popular culture to propagate socially useful ideas, in particular, the science fiction genre.In 2006, "The Guardian" described Firrell as "One of the capital's most influential public artists".Writing in "The Independent", Howard Jacobson stated, "I like words on public buildings and Firrell is a master at gauging their power."