THE subject of Mike Figgis's astonishing Leaving Las Vegas (18) is unconditional love - the truest, the rarest, and, perhaps, the only sort. The film is a virtual two-hander between a washed-up screen-writer, Ben (Nicolas Cage), deliberately drinking himself to death, and a prostitute, Sera (Elisabeth Shue), who has reached a kind of bruised acceptance of her trade. He is her trick, but instead of having sex with her, he talks to her, and they connect, then fall in love. Both have an unvarnished honesty, born of extremity and desperation. Neither seeks to change the other. "You can never, never ask me to stop drinking," he tells her. "You understand?" Her answer resembles a marriage vow: "I do, I really do"; and a piano tinkles sweetly on the soundtrack. Later he tells her that he is at ease with her job - "which is not to say that I'm indifferent, it simply means that I trust, or accept, your judgement." Among the melancholy romantic songs on the soundtrack is Don Henley's rendition of a Johnny Mercer-Harold Arlen classic: "You're gonna love me like nobody's loved me, come rain or come shine."

The movie opens with Ben in Los Angeles, stacking a shopping trolley high with bottles of booze. Cage's Ben drinks like no alcoholic we've seen in the movies before. We watch him swigging, glugging and slugging the stuff down, demolishing bottles of spirits as though they were fruit juice. He drinks in bed, in the shower, even, in one surreal sequence, underwater. Some people drink like there's no tomorrow. Ben drinks to make sure there isn't one for him. Figgis is superb at capturing the reactions of the sober world to the drunk. When Ben bursts in on a friend in a restaurant to beg him for some cash, the women at the table exchange embarrassed smirks. Sadness and pity mingle in Ben's boss's face as he sacks him. Making a bonfire of his possessions, Ben heads for Las Vegas.

As Ben, Cage gives a miraculous performance, from his puffy, sweating face to his light-footed walk, which avoids the cliche of the slow, stumbling alcoholic, as if his feet were in touch with his sprightly soul. There is self-hatred in his bravado, but he also provides crucial rays of humour in the cavernous gloom. Challenged by a heavy in a bar, he puts on a seigneurial British accent - and earns himself a bloody face. "Gifts!" he yelps delightedly, when Sera gives him parcels containing a scarlet shirt and a silver flask. Even when he falls on to a pool-side table, he manages, amid the crashing glass, a highly amused and amusing "Whoooah!".

Elisabeth Shue is equally fine - a wrenching mixture of vulnerability and control, her features feminine and pretty but also sharp and unillusioned. When she chats up a potential trick in a bar, her fake charm can't hide her genuine niceness. Her almost suppressed signals of alarm as she is abused by her Russian pimp (Julian Sands) - a little downward moue of the mouth as he slams her head against a wall - are heart-rending. Sera's love for Ben is unmistakable, radiant, but always clouded by concern - at his drinking, his self-destructiveness, and at the inevitable shortness of their time together.

Her acceptance is a virtue and a disease. It becomes "all-consuming, like a well-matured cancer" writes John O'Brien in the 1990 novel on which the film is based. Not the least boon of the movie's American success - it has won several critics' awards and looks headed for Oscar recognition - is that it has returned this harrowing, beautiful book to print (by Macmillan here). O'Brien shot himself last year, aged 33, shortly before Leaving Las Vegas was filmed. It might be facile to read the book as a suicide note, but there is a hint of a suicide's self-pity and vengeance, as well as idealism, in an ending that starkly leaves Sera "awake in the darkness". In this deep-ly moving finale, O'Brien writes: "It all became clear [to Sera], how much more deliberate his life was than hers, how he knew the one great trick that she couldn't do, and how she would fall in love with him every minute, every second, over and over again, for the rest of her life."

Figgis has recognised this wild romanticism as the keynote of the book. Despite the depravity that is the novel's subject - and which the film unflinchingly recreates - O'Brien believed in a nobility the world couldn't quite match. Sera, with her boundless compassion, is, Ben says, "an angel". O'Brien writes that she "never really understood why so many people choose contempt as the first option". Likewise, Ben, despite the direness of his straits, retains a consideration for others. The movie swoons to romantic melodies, sung by Sting, while Figgis's own jazz score is adept at moving from the screech and trembling of delirium to the lull and lyricism of love. Figgis sticks closely to both the spirit and the letter of the book, using the device of Sera talking to camera (maybe to an analyst off-screen) to allow us into her thoughts. His screenplay is often inspired. He turns a simple scene in the novel, when a crashed-out Ben is robbed in LA by a hooker, into a piece of poignant erotica as she sucks the wedding ring from his finger.

Leaving Las Vegas fulfils the promise of Figgis's earlier work, films such as Stormy Monday, Internal Affairs and Liebestraum: his jazzy energy, tender eye for relationships, feeling for sexual obsession, skill with actors, and obvious delight in an understanding of film itself, all come gloriously together. In BBC2's Close-Up series, Figgis spoke brilliantly about Godard. And Leaving Las Vegas feels more continental than British or American; it has the same jagged intensity in its acting as Last Tango in Paris. As uplifting as it is gruelling, it's an extraordinary movie.

Casting an ex-Marine teacher of ghetto kids, who else would you choose but Michelle Pfeiffer? Dangerous Minds (15), a true story and a To Michelle, With Love, doesn't make much of Pfeiffer's brawny past, for obvious reasons, but she's good enough to have us suspending our disbelief within minutes. Faced with a class that make the old Shed End at Chelsea seem a model of propriety, she exchanges her overwhelmed look and meek smile for jeans, a leather jacket and a new attitude. Soon she is weaning her charges on Bob Dylan lyrics (analyses of the narcotic subtext to "Mr Tambourine Man") and candy bars (for good behaviour). The movie is preposterous, but, except for a few schmaltzy passages when Pfeiffer offers encouragement to parents, it works. Credit should go to Ronald Bass's solid script, and John N Smith's promisingly stylish direction. You may wonder, though, at so thorough an endorsement of bribery as an educational tool.

Mike Figgis is not the only British director on top form this week. Anthony Waller's first film, Mute Witness (18), a suspense thriller set in Moscow, marks him as a talent to watch. Suspense is the word: the movie opens with a half-hour, almost parodic exercise in nerve-jangling, as a woman witnesses a snuff movie being shot, and then scarpers through corridors and lift-shafts pursued by the murderers. The woman is mute, so we have to do the screaming for her. There are holes in Waller's script, and one or two indifferent performances in a cast who are all unknown - except for Alec Guinness, in a tiny cameo as a criminal Mr Big, full of decrepit menace. But Waller directs with flair and wit (at times the movie becomes a comedy of communication); unlike so many British directors, he tells his story through pictures. His movie may be portentous and unfelt, but it entertains (and scares) the hell out of us.

The strange career of Steven Soderbergh continues: from boy wonder (sex, lies and videotape) to outcast (Kafka) to American art house (King of the Hill) - to The Underneath (15), a sleek, intelligent, if anaesthetic remake of Robert Siodmak's 1949 film noir, Criss Cross. Peter Gallagher, selfish and saturnine as ever, plays a man returning to his home town for his mum's wedding, ready to rake up the past: a girlfriend he abandoned, now courting a mobster, and a gambling addiction that destroyed the relationship. Siodmak's film climaxed with a memorable heist scene, though early on it was sluggish. Soderbergh seeks to spice things up by using a triple time scheme, intercutting the past and the present with the heist to come. The result is a coldly cerebral but absorbing take on classic noir themes such as fate and desire. The movie is about the lasting allure of old pleasures: whether it be the scent of a woman or of money.

Cinema details: Review, page 68.