Clarens (An Illustrated History of the Horror Film) is a fierce believer in the genre approach to film. And here he attempts a historical analysis that expands the familiar gangster-film genre into the ""crime movie""--any film dealing with socially-resonant crime (not the private world of psycho-thrillers). But ironically, and perhaps inevitably, Clarens is only coherent and persuasive when sticking to the genre at its earliest and narrowest: he does a shrewd, lively job of tracing the interplay between social comment and hard-boiled thrills--from D. W. Griffith to Von Sternberg's 1927 Underworld (""the first gangster film with modern credentials"") to the tough early-1930s sagas that were accused of glorifying crime (Little Caesar, Scarface) to the era of tight censorship (pro-F.B.I. dramas) to the comeback of gangster films in the guises of comedy (Lady for a Day, etc.), existential angst (The Petrified Forest), and ""relentlessly redemptive"" parables (Each Dawn I Die). But the tunnel vision of a strict genre approach leads Clarens murkily astray in the less pigeon-hole-able postwar era: he overpraises small true-genre pix (Baby Face Nelson, etc.) while faulting more ambitious, beyond-genre work (On the Waterfront); he has little fresh to say about how Bonnie and Clyde and The Godfather reverse crime-film perspectives; and his urge to expand the genre leads to glib treatments of complex work (Taxi Driver) and to the nonsensical notion that the ""conspiracy film"" (which goes back at least to The 39 Steps) is the ""final development of the crime genre."" A half-reliable survey, then, for wary film students only.