The bit in her book that readers are reacting to the most, says Louise O'Neill, is not the gang rape.

"Obviously that's just really horrific. But there's this scene, with Paul, where she just doesn't give consent. She doesn't want to have sex. She wants to go back to the party. The amount of people who have emailed me to say that scene is so disturbing, so uncomfortable . . .

"Because I think that scene has actually happened to a lot of women. They say, 'When I was 19, I didn't have the tools, I didn't know how to say no. I didn't know how to set up boundaries.'"

The experience readers keep relaying, says O'Neill, is this: "It wasn't rape, but it wasn't right."

O'Neill is the Irish author of young adult novel Asking For It. It's the story of 18-year-old Emma O'Donovan. Beautiful, happy and confident. Also, a bit of a bitch. ("I imagine them whispering to themselves once I'm out of earshot about how nice I am, how genuine, how I always seem to have time for everybody, how it's amazing that I can still be so down to earth when I look the way I do.")

Emma goes to a party. She wakes up on the front porch of her house. She's in pain and she doesn't remember the night before. But Facebook does: Slut-liar-skank-whore.

"Does it matter if you can't remember?" asks the publicity blurb, before declaring this a novel "about betrayal and consent, truth and denial, in the age of the smartphone".

It is a tale of its time.

O'Neill wrote the book after reading about the sexual assault of a drunken Ohio high school girl by two teenage football players. It became known as the "Steubenville rape". It was recorded on cellphones and shared, by the girl's peers, on Facebook, Twitter and text message.

"It was utterly horrifying," O'Neill blogs. "And yet I was weirdly fascinated by the case, by the nonchalance of those young men, their seeming conviction that they were entitled to use that girl's body in whatever way they wanted to."

Public reaction, she writes, was telling. Horror, yes. But also grief that a guilty verdict would ruin the perpetrators' promising futures and judgment of the victim "who shouldn't have put herself in that position".

O'Neill winds these threads through Asking For It. Emma is ostracised. A national talk show makes a meal of her shame. He-said-she-said-he-said. And if all of this is sounding sickeningly familiar to Kiwi readers, then the book's ending may not come as a surprise.

Almost exactly two years ago, New Zealand police called a press conference to report no charges would be laid against the self-titled 'Roast Busters' group – the West Auckland teens who came to notoriety in online videos where they boasted about having sex with drunk, underage girls.

The eventual investigation would canvass 110 girls and identify 35 young men as "persons of interest". Seven girls would make formal statements and a further 25, who police believed were victims of some form of sexual offending, would choose not to.

At that press conference, reporters were told there was an over-riding fear among the girls of bullying by their peers, and of being exposed by media.

"There was sufficient information available that confirmed their fears as a reality," the police summary said.

O'Neill had never heard of the Roast Busters case before this interview, but her response to its bare facts is swift.

"That is just so heart-breaking. It's just again so indicative of a culture in which the perpetrators of sexual violence against women are protected and inoculated and the survivors have this overwhelming sense of guilt and are afraid of being blamed. Victim blaming is such a real thing.

"There needs to be a culture shift around these attitudes. It's still very prevalent. People think that if a woman is drinking, or she's taken drugs, or she's wearing very revealing clothes or she's had a lot of sexual partners, if she's flirting with a man, that's she's somehow, you know, asking for it.

"I really think we need to have that shift where, no matter what circumstances, people also say that rape is the fault of the rapist."

Asking For It is not a comfortable read. There's the c-word on page 22. A hundred or so pages later, there's an act specifically defined as objectionable under New Zealand's Film, Videos and Publications Classification Act.

The author is aware of the censorship controversy around Into the River, the young adult novel by Ted Dawe, slammed by conservatives for its sex scenes and bad language.

"It makes me so furious," says O'Neill. "It's so worrying to think that people who need to read these books wouldn't be allowed access to them. People say to me, "Oh, your book is so graphic and I don't want my 13-year-old son reading it… what are they looking at on the internet? What are they looking at on their phone right now?"

O'Neill is tired of the judging – and that is, partly, what's shaped her book's content.

"I wanted to get away from this trope of the 'perfect victim', and that we only have a finite amount of sympathy, and in order for us to have sympathy for you as a rape victim, you need to have met all this criteria. If we hear that you had multiple sexual partners, or decided at the last minute you didn't want to, or if you were a sex worker, then we don't have sympathy for you – you're not good enough to deserve sympathy."

Her editor asked her to consider a happier ending. "I just said, 'Statistically, it's unlikely'… I grew up in a small town, and I just feel like I know that feeling of just wanting it all to go away."

Plus: "I really wanted the reader to finish this book and be so angry and furious at the way our judicial and legal system is designed, I suppose, to protect the perpetrators of sexual violence against women. Something has to change, and this can't continue to happen."

O'Neill was born in Clonakilty, West Cork. Her first book, Only Ever Yours, was acclaimed as Mean Girls meets The Handmaid's Tale; a multiple award-winning dystopian story of girls bred solely to please men; who compete to become wifely companions or used and abused concubines. Beauty, thinness – and good behaviour – are paramount. It does not end well.

"When people meet me for the first time, they're expecting me to be a dark person! It's just the way the books seem to come out… "

Dig a little deeper. At 15, O'Neill was diagnosed with an eating disorder. At 21, she was hospitalised. "I started pretty much recovering when I was 27 and I'm 30 now and you know, it's still… I'm very well able to manage it, and I'm very healthy and I'm at a healthy weight, but I think maybe it's a bit like being an alcoholic. You should take one day at a time. Each meal at a time."

Writing is catharsis-therapy-survival. In a recent piece for the Irish Examiner, O'Neill reflected on her own teenage years.

"I have revisited my old school many times now and I feel a little dizzy walking through the front door, as if the veil covering the space/time continuous becomes translucent, as if I might fall back into the past. Some students always me questions: 'Did you like school?' 'Did you like living in a small town?' 'Did you fit in when you were our age?' And I know what they're really asking. 'Am I going to be okay?' 'Is this going to turn out alright?' 'Will I survive this?'"

"The thing is," says O'Neill, "the older I get, the less I need to be perfect.

"It's such a clichéd attribute for people with eating disorders. You're an over-achiever and very driven and a real perfectionist. The problem with perfectionism is it paralysed me for years. I thought, 'I want to write a book, and I'm not going to unless I know it's going to be a masterpiece and I know it's going to win the Booker Prize and have people raving about it.'"

Rock-bottom, on a visit home from New York where she was working as an intern to the senior style director at American Elle, her father asked what would make her happy. Writing, she realised.

"And once I started writing, it was like something unblocked in me. It was like I was a shadow and sort of transparent, and the more that I wrote, the more that I became a real human being – for want of better words!"

It's 7.30am in Ireland, and O'Neill has just made herself laugh. Last night, she was "super drunk". Tonight she'll wear Irish label Lennon Courtney to a literary event. Later that week, she will ponder: "Three months living in Dublin and I still haven't bumped into my ex boyfriend or that awkward Tinder date. God loves me."

We know all of this because O'Neill is a selfie-posting Twitter addict who drinks and thinks about boys one minute and campaigns for abortion rights the next.

Once, she wanted to be an actor. For a time, she wanted to be Barbie.

"Yes, yes I did! You're given this doll and she seems so beautiful and then you grow up and the same ideal of beauty is represented to you – very, very tall, very thin, big breasts, blonde and, a lot of the time, white.

"I just felt I was failing to meet those kind of standards. I started thinking what if I was five foot? What if I was black? You're not seeing anything that looks anything remotely like you… I can't imagine how difficult that must be to navigate a world that wants to make you feel like you're less of a human being just because of your genetic make-up. What do you do?" asks O'Neill.

"People ask me what needs to change. It's kind of hard to say we should change everything. Just burn this entire system down to the ground and start again."

Asking For It by Louise O'Neill (Hachette New Zealand, $24.99)