If you've ever wondered why young people take drugs, read Olivia Gordon's book, The Agony of Ecstasy. She has written a thoughtful, sometimes brutally honest, account of her experiences. It will resonate with many who have taken drugs and provide an insight for those who haven't.

Olivia tried cannabis, speed and LSD, but her description of taking ecstasy is what gives some idea of how fantastic drugs can be.

"I was overcome by an unspeakably massive wave of passion that still sends a shiver down my spine," she writes. "A sense of effervescent excitement showered down beautifully into me like a snowstorm."

Having touched paradise, it was all downhill from thereon, as the ecstasy induced a severe depression that lasted several months.

Olivia makes clear from the beginning that The Agony of Ecstasy is neither social history nor a story of "a 'my drug hell' sensation" -- rather, it is a warning of how ecstasy affects some people.

When we met at her parents' home in North Oxford, I asked her whether what she went through applied to other people. "Yes, since I've been writing the book several people have said to me, 'Oh, I had a similar experience'."

The book is quite ambiguous about drugs. "I really tried to make it balanced," Olivia said. "I felt when I was writing it that people were so polarised. People will either say 'Oh how stupid, you took drugs' or they'll say 'I'm a real raver and you don't know what you're talking about'."

Olivia herself would never take hard drugs again, particularly ecstasy, which she sees as a poison. She also believes there will be a backlash against it.

"It's almost like you're not allowed to criticise it and some people say whatever fears you have are just tabloid scare-mongering. That is why I wanted to be balanced."

Although Olivia had a happy childhood, she was a typically rebellious and naive teenager. She writes very well of her time at school in Oxford and the difficulties of fitting in -- although she declined to tell me which schools she attended here.

Her parents are South African and she visited Cape Town a lot over the years, making close friends who accepted and loved her for who she was. They started experimenting with hard drugs for philosophical reasons and Olivia joined in. Would she have got so heavily into drugs if she had stayed in Oxford?

"No, I'm sure I wouldn't, because my friends here were all much more conventional, though they did take drugs sometimes." she said. "I think it was to do with the people I met in South Africa. They really seemed to care about ideals and philosophy, truth and things like that."

When I point out that there are people here concerned about such things, Olivia said: "Yes, but I didn't know any of them. Maybe if I'd met someone here who was interested in philosophy at that age who wasn't taking drugs, I could have taken a totally different path."

Olivia's parents are both academics, although her mother now writes biographies full-time. They come across as liberal and loving in the book, providing a stable background. I asked Olivia why they didn't force her to come home when they found out about the drugs.

"They have never been like that with me. It wasn't that they were happy with me taking drugs, but basically by the time they knew I was, I was already depressed and had stopped it."

They were very shocked when they read her book, not having realised quite how extensive her drug-taking had been, nor how deep her depression. Olivia, now 25, has suffered no long-term effects from the drugs. She works in London as an editor and staff writer in health-care publishing. Her book was published through sheer serendipity.

She was offered a contract by her publisher after he saw an article she had written on ecstasy in London's Evening Standard. She plans to continue writing and her next project is a novel.

Is she worried about being labelled? "I'm sure a lot of people will judge me. I've just got to accept that. I'm not too worried." As for Oxford, having hated the place as a teenager, she would now love to come back.

"It's so peaceful, so much space and privacy compared to London." She studied English at Cambridge University and when I ask which place she prefers, she replies: "I think I prefer Oxford as a town" and smiles.