Australian novelist Helen Garner will lead a diverse line-up, including Salman Rushdie, Dave Eggers and astronaut Chris Hadfield, at a remodelled Melbourne writers' festival next month.

Organisers of the 2014 iteration of the event, now in its 29th year, have secured a number of major drawcards while expanding the scope of the festival to include tram rides, music gigs and secretive, intimate talks held in caravans.

Garner, author of Monkey Grip, The First Stone and The Spare Room, will deliver the festival’s opening night address on 21 August. She will talk about her latest book, This House of Grief, which is an account of the trial of Robert Farquharson, who was convicted of drowning his three sons by driving his car into a dam in Victoria on Father’s Day in 2005.

The Booker prize-winning Rushdie will deliver a keynote speech on 28 August on the “freedom to write”, which draws upon an overarching theme of freedom for this year’s festival.

Astronaut Chris Hadfield will host an interactive talk on his adventures in space and his book, An Astronaut’s Guide to Life on Earth. It’s unclear whether Hadfield will take the opportunity to reprise his epic gravity-free rendition of David Bowie’s Space Oddity.

Influential US author and publisher Dave Eggers will preview his new book, while organisers are attempting to replicate the impact of blogger Tavi Gevinson’s appearance last year by featuring Maria Popova, creator of the popular Brain Pickings website.

The line-up of 400 “authors, thinkers, commentators and creative artists” is rounded out by the likes of British novelist Philip Hensher, The Interestings author Meg Wolitzer, and the Guardian’s own Luke Harding, who will discuss the Edward Snowden leaks.

There will be plenty of weighty conversation on topics such as climate change and civil liberties. The political world will be represented by former prime minister Malcolm Fraser, former foreign minister Bob Carr and ex-Greens leader Bob Brown.

But it’s the tweaked format itself which organisers hope will lure new attendees. Audiences of just five people will cram into a caravan to speak with a secret guest writer, while "lit hop" will allow people to take a literary journey through Melbourne on the 96 tram.

There will be a cabaret celebration of bon vivant Welsh poet Dylan Thomas, who would have been 100 this year, and the sonnets and soliloquies of Shakespeare will be given a “rock ‘n’ roll twist” at the Trades Hall.

Festival director Lisa Dempster told Guardian Australia that the line-up and format aim to “democratise” literature. “The Melbourne writers' festival has always championed writers of different genres, but I want to take the festival and bust it open to all kinds of readers,” she said.

“What people call high literature is absolutely vital to a civilised society, but these days people consume literature in so many different ways. I wanted a program that talks to all different kinds of readers and people who aren’t readers.

"For example, I think people writing for TV today are some of the best writers out there and to have Emily Nussbaum, the TV critic of the New Yorker, out here speaks volumes of where TV is right now.”

Dempster said this year’s festival will have an “increased energy”, with plenty of late-night events.

“Writers' events in general tend to be quite traditional in their formats,” she said. “Panel discussions are very important but I want to make literature fun. So there will be lots of other things to do, such as conversations in a caravan, book swaps, talks, parties, all kinds of things. I hope that energy will show to our audience and open it up to people of all ages.”

• Melbourne writers' festival runs from 21-31 August in venues across the city