Meg Rosoff might be known as a successful author for young adults, but it’s not necessarily a category with which she’s comfortable. ‘Recently, I re-read To Kill a Mockingbird for its 50th anniversary,’ she says. ‘If that was published now, it would be marketed at teenagers. People have this category for teenage fiction that never used to exist, that a lot of books are now slotting into.’ The writer, whose 2004 debut How I Live Now won the Guardian Children’s Fiction Prize and whose latest novel is the Isabella Bird-inspired Victorian adventure The Bride’s Farewell, is among a host of authors primarily associated with a young adult audience set to appear at Charlotte Square Gardens. The line-up includes Louise Rennison, Robert Muchamore and Patrick Ness but among the most keenly anticipated figures is Australian artist Tohby Riddle, this festival’s second Illustrator-in-Residence.

Though primarily known for his children’s picture books, Riddle’s only novel for young adults, The Lucky Ones, has been widely lauded. But while many writers consider teenagers a tricky audience to please, Riddle’s approach is a pragmatic one. ‘I really only had one rule: don’t try and be cool. Try to remember what it felt like to be a teenager and tell a story in a companionable way that’s authentic and sincere.’ John Green, another high-profile attendee, agrees: ‘I think that teenagers are very sensitive to inauthenticity. They are keenly aware when they’re being condescended to. But you face the same challenge when you’re writing for any audience. You don’t ever want to be seen to fail to understand the complexity of someone else’s life.’

Green’s books, including Looking for Alaska, Paper Towns and his newest, Will Grayson, Will Grayson (a collaboration with fellow American David Levithan), have attracted much praise in the US. Unlike Rosoff, who is adamant that she does not ‘write for children or young adults or any particular audience’, Green is more embracing of his teen fiction tagline. ‘I really care about teenagers in a way that I don’t care about adults. I feel like it’s such a privilege to have a seat at the table of young people as they form their values, as they encounter for the first time the big questions of our species. Plus, Philip Roth has a great gig but he doesn’t get an email every day saying, “This is the best book I’ve ever read”.’

Much of Green’s fame stems from his part in YouTube’s popular vlogbrothers channel, a series of videos he creates with his brother Hank that have featured everything from accessible analyses of current affairs to readings from The Catcher in the Rye. Cumulatively, their videos notched up nearly 80m views between January 2007 and June 2010 and it’s this social media success that publishers and other teen fiction writers are looking towards to stay abreast of their ever-changing audience. On this side of the Atlantic, teen and tween author Cathy Cassidy enjoys a similarly robust online presence and is enthusiastic about its advantages. ‘The whole internet way of networking and communicating is so natural for young people that I think anyone who is not using it is missing out, especially when you encounter somebody who really gets what you’re trying to do or really connects with your story.’

In addition to embracing technology, however, writing convincing young adult fiction is about learning from books that have already enjoyed generations of young adult readers. Rosoff cites Flambards author KM Peyton as one of her favourites, while Green asserts that ‘many coming-of-age novels have their roots in Jane Austen’. Riddle also claims Salinger and Kerouac as models for success. But, according to Cassidy, it’s not what teenagers read but the fact that they read at all which is important. ‘I think people are too concerned with what children should be reading. Whether you do it on an iPad or the internet, the medium doesn’t matter. Loads of girls are reading Twilight and that’s fine. You should read what you want to read.’

Meg Rosoff, 14 Aug, 3pm; John Green, 15 Aug, 4.30pm; Tohby Riddle, 15 Aug, 6pm, £10 (£8); 16 Aug, 10.30am, 4.30pm; 17 Aug, 1.30pm; Cathy Cassidy, 17 Aug, 10am; All events at Charlotte Square Gardens,
0845 373 5888, £4 unless stated.