I've only just sat down to lunch with Janey Godley in the restaurant of a chi-chi London hotel when an over-enthusiastic waiter knocks over a wine glass, shattering fragments into her lap. Kindly, she lays a hand on his arm and cuts through his flustered apologies, saying: 'Don't worry, love; if no one made mistakes there'd be no children.' In the same breath, she turns to me and says, with mock affront, and loud enough for other diners to turn around: 'I ran a pub in Glasgow for 15 years and I have to come to a posh London hotel to get glassed.'

It's this combination of compassion and clear-eyed wit that characterises Godley's comedy and has made her such a breath of fresh air on the stand-up circuit. Those who saw her on E4's Big Brother-esque Kings of Comedy last year will be familiar with her mischievous laugh, excitability and talent for saying exactly what she thinks while managing not to offend. Almost every reviewer has described her as unique, both because of her unusual route into performance after a difficult background in Glasgow's most deprived areas and the unflinching candour with which she tackles subjects that many people might consider beyond the reach of comedy - child abuse, domestic violence and murder among them.

Until her Edinburgh Festival show last year, few people realised how much of her dark materials were based on her own experience. Now 43, she has expanded these tales into a remarkably engaging and fluently written memoir of a life that makes the McCourt family look like the Von Trapps. To summarise: grew up with hard-working but alcoholic father and feckless, debt-prone mother; regularly abused and raped by her uncle for most of her childhood; left school early; married at 18 into notorious Glasgow gangster family; husband prone to fits of depression and physical violence; one brother HIV positive heroin addict; mother murdered by violent boyfriend; Godley and her husband finally arrested and imprisoned when a police raid revealed their house to be packed floor to ceiling with small arms and explosives.

Was she aware that, in retelling her experience so publicly, she was following a tradition that some see as a kind of pornography of tragedy?

'Yes, I felt a bit creepy. I didn't want it to be like A Child Called It - that whole literary snuff thing. I'd be scared to say that I hope it will help other people who've been abused because that's a big responsibility, and my way of dealing with it might not be right for someone else. I steer away from that kind of thinking.'

Given that it was only late in life that she even told her father and brothers about the abuse (which also affected her older sister), was she worried about how her family would respond to her writing so frankly?

'There's no chance any of them will contradict me,' she says, grinning, 'they cannae write. My sister read it and loved it, but she said she saw things very differently. Not that it didn't happen, but it's like two people seeing a car crash - you remember different details. My dad is very proud that I didn't get an education but I've written a book. I feel for them a wee bit. They're not used to talking to the press and I think they don't know the extent to which people will be reading and talking about them.'

Godley's life began to change direction after 'Old George' Storrie, the patriarch of her husband's gangster family, died suddenly, leaving his seven sons fighting like cats in a bag over his ill-defined will. Godley and her husband, Sean, who were buying out the pub they tended for Old George, and which their hard work had made highly profitable, found themselves conspired against by the other brothers and decided their only hope for a better future for themselves and their young daughter was to leave the gangster clan.

'That's what happens when you marry into a bunch of men who've never understood that a woman's allowed to talk loud,' she says, matter of factly. Her natural assertiveness and independence of mind provoked malice from her brothers-in-law all her married life, directed both at her and her little girl. 'My husband always says he never married a woman like his mother, he married a woman like his father. That was exactly true: Old George and I were very alike; he was funny and he was a storyteller.'

At the age of 33, she fell by chance into performing and discovered that running a pub in the troubled Calton area of Glasgow, where drug deaths, violent crime and murder were everyday events, was a far better training ground for the comedy circuit than Footlights.

'I was funny behind the bar,' she says, with no trace of bragging. 'I'd get big, burly men come in shouting and I'd have to shut them up and the best way to do it was to have an answer for everybody. Then one night, this man phoned me and said, "We're having an open mike night and you're really funny; why don't you give it a go?" I didn't know what an open mike night was, but I went along and won the gong. The stand-up became addictive. When I started headlining clubs, people would be amazed at my crowd control because I could shut up 700 loud drunks, but that's just being a good barmaid. When I started doing comedy, I felt like I'd come home.'

Her raw material impressed comics such as Stewart Lee, whose advice after seeing Godley at the Edinburgh Festival was to concentrate on talking about her own life, which set her apart from other comics. Since then, she's played in New York and New Zealand, earned comparisons with Billy Connolly and just had her first one-woman straight play at the Soho Theatre. Perhaps most surprising is that she is still married to Sean, who was deeply troubled in his youth, when his nickname was Mad Eyes.

'Twenty-five years this year,' she muses. 'He's no' that man any more. He had his own demons but he's changed. That sounds like I'm making excuses for a bad man, but we were two fucked-up people who should never have been married at 18.'

Does he mind that she's presented such a naked portrait of his depression and violence? 'He hasn't read the book and he won't, but he says, "I know you'd write the truth." He's very proud of me but he says, "If you were a secretary, I wouldnae come and watch you at work. It's your job and I'm not interested." We live very independent lives now but he'll say, "I know you never wanted to be a barmaid and you had to do it for 15 years, so now you must do what you want to do."'

What she wants to do next is more serious acting, though she's also at work on a novel and a film idea and taking a new show to the Fringe this year. 'I don't know what I'm supposed to be,' she says. 'Anyway, who says you have to be just one thing?' After writing the book and last year's show, she wants to leave that material behind. But has the experience been a way of putting the past to rest?

'There was one moment like that,' she recalls. Her publisher's lawyer asked her to find 'the man who murdered my mum' to make him sign a waiver. 'I looked him up at the genealogy department in Glasgow and it turned out he'd been murdered years ago.'

What do you think you would have said to him, after all this time, if you had found him? I ask. Without hesitation, she says with cheery steeliness: 'I'd have said, "Sign that, you fucker." And I'd have made him do it.'

· Handstands in the Dark by Janey Godley, Ebury, £14.99.