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Next time you are on a beach or a crowded train, look at the reading matter on display. There's a high chance you'll spot Gone Girl by Gillian Flynn, The Unlikely Pilgrimage of Harold Fry by Rachel Joyce, and maybe The Light Between Oceans by ML Stedman; a couple of years ago it would have been One Day by David Nicholls. All are compelling reads, in their different ways, but what does it take for a book to become a best-seller?

"These things tend to follow a pattern," says Will Francis, a literary agent at Janklow & Nesbit. "Right now, everyone is trying to find the next Gone Girl. Publishers get particularly excited about high-concept novels and debut thrillers. But there's always an element of spread-betting in publishing. Even when a book has a high chance of success, it's less than 50 per cent."

With such poor odds, it's no surprise that publishers put such effort into securing a return on their investment. When Susanna Wadeson, at Transworld, bought The Unlikely Pilgrimage of Harold Fry back in 2011, she assembled a team to work on the launch.

"We looked at Before I Go to Sleep by SJ Watson, which had been a best-seller for us, and analysed what we would do differently for Harold Fry," says Wadeson. "We decided it was the sort of book that people would want to discover for themselves, rather than be told how good it was, so our jacket and blurb – and early campaign – were understated.

"And we 'hand-sold' it, giving copies personally pre-publication to literary editors, bloggers and key bookshops, rather than making a big corporate noise about it."

Wadeson also had a secret weapon in Joyce, her good-looking author, who charmed the sales reps. She became an integral part of a campaign that centred on the route Harold Fry walks from Kingsbridge in Devon to Berwick-upon-Tweed, where a former colleague is dying. Bookshops and early readers along the route were encouraged to tag themselves on a map on Facebook, and Joyce visited a number of the bookshops. "Bookshops tried to outdo each other with window displays," recalls Wadeson. "One even baked a cake in the shape of Fry's walking boots."

Buoyed by tips from several literary editors in their 2012 New Year predictions, the book was soon shortlisted for the Desmond Elliot prize and longlisted for the Man Booker, endorsements that helped build momentum for the paperback launch this January, when it was also chosen for Richard & Judy's book club, which retains considerable influence, thanks to its relationship with WH Smith. To date, Harold Fry has sold more than 325,000 print copies in the UK alone.

For every success story like this there are, of course, many failures, and it's fair to say that the road to best-sellerdom is littered with casualties.

The British rights for The Age of Miracles by American author Karen Thompson Walker were bought for a reported £400,000. Despite a big campaign, the book is not performing as well as expected. It ticks many of the best-seller boxes – high concept (the rotation of the earth is slowing, days and nights grow longer), terrific reviews, film deal, big spend marketing campaign – but it is struggling to earn back its advance.

One source said that sometimes publishers are too keen to publicise a high advance for a novel. "I've seen it backfire and work against a book. It can feed resentment and cynicism among reviewers and industry people who should be catalysts for a book's early success."

For those few books that do break through, the benefits can be self-perpetuating and exponential. A book that makes it on to the New York Times bestseller list will automatically begin to sell more.

Combine that with word of mouth, that marketing tool that can't be bought, and you just might have a best-seller on your hands.

Jon Stock's latest thriller, 'Dirty Little Secret' (Blue Door), is out in paperback on August 1