Most of the books and films I love walk a knife edge between romance and cynicism, and I wanted One Day to stay on that line. I wanted it to be moving, but without being manipulative. I wanted it to be quite a big emotional book, funny and sad, and for people to respond out loud. That can be quite a nerve-racking thing to strive for. You don't want to tip over into mawkishness or be unamusing when you're trying to be funny.
One Day has quite a following among 17, 18 and 19-year-olds, which is interesting and unexpected. It obviously sums up people's anxieties about the future: their intentions and idealism. I think a connection with people's own lives is important [in a hit novel]. It's not necessary; some of the most successful books at the moment are fantastical and otherwordly. But the fact that people connected One Day very specifically to their own friendships, relationships, regrets and anxieties about getting older was important.
I've only ever been recognised in the street once. In Sweden, strangely. There's no photograph of me in the book. And as an actor I was uniquely bland and unmemorable.
I'm desperate that the next book shouldn't disappoint people, but there's an expectation that it might not be so well-read, that critics might be a little harsher, that anything which sells less than One Day might be perceived as disappointing. To sit down in the morning and for those to be the first thoughts in your head can make it difficult to write.
The only thing I know about the next book is that it won't be a love story set over 20 years. It may have a romantic element but it won't be primarily a romantic comedy. I'm 45 now and I have a family, so first dates and the awkwardness of relationships in your 20s are quite distant to me. I'm interested in mothers and daughters, fathers and sons. One thing that it will have in common with One Day is a mixture of comedy and dramatic material.avid Nicholls: 'A lot of novelists improvise, and I'm quite envious of that ability'
Full story at The Independent. 
It's death to think about a perceived demographic when you write a novel. With One Day, I just wrote the book that I wanted to write; I didn't think "I might have to expand on this section to appeal to men" or anything like that. I was anxious that it might only make sense to people aged between 38 and 44, who lived in London and had been to university or had certain political and cultural experiences. Thankfully that turned out not to be the case.