His debut novel "The Cuckoo Boy" was published by London publishing house To Hell with Publishing in May 2010. The novel tells the story of an unusual boy adopted into a middle-class British family anxious to conform, with dangerous consequences. Parts of the novel were inspired by the James Bulger case. Literary charity Booktrust wrote that Grant Gillespie "writes beautifully about imagined dreamscapes and viewing the adult world with a child’s eyes."