At a time when the output of Hollywood has plummeted to an unparalleled level of infantilism, Scorsese's enjoyable master-class serves as a useful reminder of the industry's glorious past, when even low-budget B movies could be works of startling originality. As Scorsese remarks: "Over the years, I have discovered many obscure films and sometimes these were more inspirational than the prestigious films that received all the attention."

Though he singles out such shoestring classics as Jacques Tourneur's Cat People, which cost pounds 134,000 in 1942, and Edward G Ulmer's Detour (1946), shot in six days for $20,000, Scorsese also acknowledges a debt to De Mille's biblical blockbusters: "His later epics are the ones that made an indelible impression on me, particularly his own remake of The Ten Commandments, which I have seen countless times."

Originally a script for two BFI documentaries on American cinema, Scorsese's text is simple and to the point: "First and foremost, film noir was a style." It is augmented by excellently reproduced black-and-white stills from films both famous and obscure: John Wayne striding into the void at the end of The Searchers, Gene Tierney as a smouldering murderess in Leave Her to Heaven; Gaby Rodger's screaming face up-lit by a radioactive glow in Kiss Me Deadly.

Scorsese's taste in dialogue is equally sure. Particularly outstanding is the stiletto-sharp banter from Sweet Smell of Success, the mini-lecture on criminality and big business from I Walk Alone (it would fit into Scorsese's own Casino) and the shivery, unforgettable exchange which climaxes Clint Eastwood's Unforgiven. Sheriff (Gene Hackman): "You'd be William Munny out in Missouri. Killed women and children." Munny (Eastwood): "That's right. I've killed women and children. Killed just about everything who walks or crawls at one time or another. And I'm here to kill you, Little Bill."

Though Scorsese insists that "the film director has to be, first and foremost, a team player", the book is a glorious celebration of the auteur theory - the insistence on the primacy of the director first advanced in Cahiers du Cinema and elaborated by the American critic Andrew Sarris. However, few films today show any sign of authorial stamp. It is a sad reflection that Scorsese feels it necessary to advise the nerdish young turks who dominate modern Hollywood to see films from the past: "I'm always looking for something or someone that I can learn from."