The hell-for-leather pace of this memoir by the maverick actor Pete Postlethwaite is explained by the fact that death was knocking fairly insistently at the door as he put it together. When, finally, the film star's luminous energy began to wane last year, he invited the writer Andy Richardson to help him finish the project. This means that many of the earlier chapters  those dealing with Postlethwaite's youthful adventures and his career in subsidised theatre  have the speed and sketchy detail of anecdotes remembered in the pub. Undoubtedly, this was a man who spent a lot of time in pubs. But after reading this book, you come away with a sense that, given more time, Postlethwaite would have chosen a more completist approach to his own story.

Certainly, his attitude to acting was always perfectionist, if not obsessive. At one point, he recalls working on Brecht's The Good Person of Szechwan with co-star Bill Paterson, who is shocked to see the number of squiggles, queries and underlinings covering Postlethwaite's script. In contrast, Paterson's copy was marked with a couple of margin notes.

Time and again, the Warrington-raised star of Distant Voices, Still Lives, In the Name of the Father, The Usual Suspects and Brassed Off emphasises his passion for getting his acting right. Even faced with his final film role, when cancer had limited his capabilities, Postlethwaite recounts his fiery rejection of a director's suggestion that the shooting of a scene be altered so he could sit in a chair. There was no point for him, he said, if he was not improving a film.

Such total commitment made playing the violent father in Terence Davies's masterpiece Distant Voices, Still Lives taxing. It upset him to have to identify with the character. "If you don't connect with the character, then you are on the road to superficiality and audiences always sniff out a phoney," he told himself. It was this vocational devotion that eventually earned Postlethwaite the rather burdensome label of, in Steven Spielberg's words, "best actor in the world". The Hollywood director was happy to use him whenever he could, apparently offering him the lead part in Saving Private Ryan before Tom Hanks came in as second best. And it was on the set of the Spielberg franchise The Lost World: Jurassic Park that Postlethwaite records modestly checking himself and marvelling at his rise to fame with the words: "It is a long way from Warrington."

The son of a caretaker, Postlethwaite trained at the Bristol Old Vic and then became one of a stellar group of talents, including Bill Nighy, Jonathan Pryce, Alison Steadman and Postlethwaite's then-girlfriend Julie Walters, who all learned their craft at the Everyman Theatre in Liverpool in the 1970s.

The camaraderie experienced there clearly remained important throughout his career. Reunited with Steadman for the West End production of The Rise and Fall of Little Voice, Postlethwaite writes of his pleasure at working with her again and of the steady arm he literally offered her each night on stage. Fearful of a blackout stipulated in the lighting cues, Steadman coped by reaching out for Postlethwaite's arm to guide her up the stairs at the back of the set.

Yet the comradeship of the Everyman was not enough to prevent a nervous breakdown induced by stress and illegal drug use during his period with the company's Van Load touring troupe. Paranoia struck the young Postlethwaite during a production of Arnold Ridley's trusty theatrical vehicle, The Ghost Train, which was put on to please the masses on a visit to Wales. Unhappy with the direction, Postlethwaite became convinced everyone was talking about him and suddenly walked off stage and disappeared for several days. The company was also working on a production of the disturbing play One Flew Over the Cuckoo's Nest , which didn't help.

Restored to sanity, although by his own admission still for a long time a "bohemian, beatnik, oddball, kaftan-wearing, reefer-smoking whacko", Postlethwaite gradually moved away from the stage to film. "I realised that film had an extraordinary ability to transmit purity of thought. If you're thinking nothing but the thoughts that are in the character's mind, then that is what the people in the cinema see," he writes. Endearingly, though, he sums up the appeal of his own acting as the contradiction between his face ("like a fucking stone archway") and his performance: "How can somebody who looks like a rugby prop forward actually be sensitive?" he imagines his audience asking.

In the year or so leading up to his death from cancer this year, Pete Postlethwaite had been working on an autobiography, and this has now appeared, sympathetically ghostwritten by Andy Richardson. It is an extrovert, tender, charming and unselfconscious book, with some extraordinary, hell-raising and hair-raising anecdotes. Reading it revived the sadness I had on hearing about his death, particularly the last, remarkable chapter about his final illness, recounted as it was happening, like a sort of liveblog.

I hadn't quite grasped that before he became a screen icon, Postlethwaite was basically the rock'n'roll wild man of 1970s/80s subsidised theatre: a cheerfully uncaged party animal who made Dennis Hopper look like Margaret Rutherford, yet always showed up on time for rehearsals, where a succession of thin-lipped Oxbridgey directors would find every line of their interpretation, and every inch of their stage blocking, getting vigorously challenged by an actor who knew and cared more about Shakespeare than they did.

This young British stage performer at the Liverpool Everyman, the Bristol Old Vic and the RSC, a cradle Catholic from a working-class family in Warrington, with what he calls "a face like a fucking stone archway", became in the 1990s the Oscar-nominated screen star of movies such as Terence Davies's Distant Voices, Still Lives, Jim Sheridan's In the Name of the Father playing Giuseppe Conlon opposite Daniel Day-Lewis, and Bryan Singer's cult thriller The Usual Suspects.

Despite his dad evidently being the gentlest and most caring parent imaginable, and being himself a kindly and lovable man, Postlethwaite came to prominence playing agonised and sometimes scary father figures. In Davies's autobiographical Distant Voices, he was reportedly so compelling that Davies sometimes needed to sit on his lap, child-like, between takes. Steven Spielberg called him "the best actor in the world", and in one throwaway line, Postlethwaite reveals that Spielberg wanted him, not Tom Hanks, to star in Saving Private Ryan. Postlethwaite fancied a British tour of Macbeth instead.

Postlethwaite can, however, be a bluff and unrevealing narrator. Insights into his life and personality sometimes have to be read between the lines. This is particularly the case with regard to his love affair with the Liverpool Everyman's sparkling up-and-comer Julie Walters.

The affair began as they acted together as part of the Everyman's Van Load touring company in the 70s and finished just as her career was taking off with Willy Russell's Educating Rita, leaving his own career, at that time, way behind. Without describing his feelings much, or really at all, Postlethwaite sadly concludes that he was "incompatible" with the emotionally maturer Walters and signs off on the subject: "It was wonderful to see how successful Jules became; she enjoyed an inexorable rise . . . our time was through. I wished her all the best. I was thrilled for her, genuinely so."

Is there a quiver of remembered heartbreak there? His delicacy probably springs from respect for his current partner Jacqui Morrish, for Walters's privacy, and simply from a sense that this is not as important as the work. For Postlethwaite, acting was not a matter of calculated celeb-careerism, but an unfashionably passionate vocation.

Yet some of what he called his relative emotional immaturity comes across in his jaw-dropping off-stage high jinks. Postlethwaite liked a drink: seven or eight or nine pints were not uncommon in an evening, and there were times when he was getting through a Constable-sized haywain of weed. While at the RSC, Postlethwaite crashed his MGB roadster under the influence. At the time he was renting a cottage outside Stratford where he and director Nick Hamm would drop acid. Maybe our young RSC players stick to Diet Coke nowadays, but that was the way they rolled back in the 80s. There is no talk of therapy or substance-abuse counselling, though Postlethwaite quietened down when he got together with Morrish.

He seems to have come unstuck just once: during a production in Aberystwyth of, bizarrely, the ultra-trad repertory piece Ghost Train, by Arnold Ridley (the playwright who later became famous playing the ageing Private Godfrey in Dad's Army), Postlethwaite succumbed to a ganja-induced paranoid anxiety attack on stage. He thought everyone was out to get him, stormed out of the theatre and his part had to be taken over, then and there, by a young Bill Nighy. Quite a night. I wish I had been there  in fact, I wish I had seen Postlethwaite's blistering performances on stage as well as on screen. This book reminded me what we're all still missing.