Consider some of McDonagh's other theatrical work, like The Cripple of Inishmaan, The Beauty Queen of Leenane, and A Very Very Very Dark Matter, or films like Seven Psychopaths and Three Billboards Outside Ebbing, Missouri.
Consider the work of other practitioners of "in-yer-face theater," such as Sarah Kane, or other dark fairy tales, such as the retellings in Angela Carter's The Bloody Chamber.