"What a long, strange trip it was. At the end of Easy Rider, when Wyatt tells Billy, 'We blew it,' he would be proved correct, although it would take over a decade to see it."

Peter Biskind's vast, exhausting dissection of 70s American cinema is at once thrilling and dispiriting. That delirious, dangerous era when auteur wasn't a dirty word and talents as diverse as Scorsese and Schrader, Coppola and Altman, Hopper and screenwriter Robert Towne were newly minted. Taxi Driver, Chinatown, Apocalypse Now, Mean Streets, Blue Collar, Nashville...the list sometimes seems endless.

But at what cost? Sometimes Biskind's book feels like it's all cost. Someone, it wants to say, had to sell their soul to be this good.

Look at that list again. Scorsese's stuck in a rut between Academy-pleasing and self-parody. Altman's hit on a one-good, two-bad formula. Hopper's a joke. And Coppola's directed Robin Williams, for Chrissake. Schrader's still doing business, but who's watching?

And yet it all started so optimistically. They're all here, plus George Lucas, Spielberg, the almost forgotten Hal Ashby, that hack William Friedkin and the very very odd Peter Bogdanovich. Biskind argues that what they had was community: the need for film. Scorsese made Mean Streets because he had to. Schrader wrote Taxi Driver when he didn't know what else to do. And Bogdanovich was a blazing new talent, which, I confess, seems extraordinary now he can't get arrested.

But that was his fault, Biskind says. And he doesn't spare the blushes. Egos run rampant, money and coke are plentiful, and these capricious but socially conscious individuals to a man (and it was always men) reverted to chest-beating form: drugs almost killed Scorsese; a loaded gun comforted Schrader enough to sleep; Friedkin's hubris strangled him; Altman was the nasty-drunk; Hopper a living, breathing cartoon. The book is scurrilous without being prurient.

The thesis - and it's hardly startling - is that Hollywood was better off run by creatives than bag men: success begets money, begets madness. Makes you lazy, complacent. Makes you the thing you most despise.

The decade drew to a close with the rise of Don Simpson and the über-producer and with it, as Bogdanovich sighs, "the cinema of the director went into eclipse...There was a general movement away from the auteurism toward producer-oriented movies." Take George Lucas, for example, pure cineaste turned hollow entertainer by a single sip of success. A salutary lesson from the decade when, as the doyen of film criticism Pauline Kael had it, "Movies seemed to matter." You are unlikely to find a better book to explain why.