The hard-boiled private detective is among the most recognizable characters in popular fiction since the 1920s - a tough product of a violent world, in which police forces are inadequate and people with money can choose private help when facing threatening circumstances. Though a relatively recent arrival, the hard-boiled detective has undergone steady development and assumed diverse forms. This critical study analyzes the character of the hard-boiled detective, from literary antecedents through the early 21st century. It follows change in the novels through three main periods: the Early (roughly 1927-1955), during which the character was defined by such writers as Carroll John Daly, Dashiell Hammett and Raymond Chandler; the Transitional, evident by 1964 in the works of John D. MacDonald and Michael Collins, and continuing to around 1977 via Joseph Hansen, Bill Pronzini and others; and the Modern, since the late 1970s, during which such writers as Loren D. Estleman, Liza Cody, Sara Paretsky, Sue Grafton and many others have expanded the genre and the detective character. Themes such as violence, love and sexuality, friendship, space and place, and work are examined throughout the text.