Want to write a string of bestsellers and spark endless romantic box-office hits? Here’s how:

Nicholas Sparks is more than just a best-selling author of sappy romantic fiction; he’s a one-man pop culture phenomenon. He has sold a reported 97 million books worldwide, and the films based on those books have so far have grossed not far short of $1bn.

The first Sparks adaptation was Message In A Bottle in 1999, with Kevin Costner and Robin Wright as the couple united when her journalist finds his letters in a bottle to his dead wife (he dies at the end). That was followed by A Walk To Remember in 2002, where Shane West’s bad boy falls for Mandy Moore’s cancer-stricken teen (she dies). But the one that really showed how big these films could be was The Notebook, making teens swoon since 2004 (Gena Rowlands and James Garner both die).

It took a while for the cult appeal of The Notebook to become clear, but since then we’ve had a steady stream of Sparks adaptations. 2008’s Nights In Rodanthe skewed a little old, but the more recent efforts and their younger casts have hit a steady rhythm. After two films in 2010 – Dear John and The Last Song – there has been one movie a year since 2012, in The Lucky One, Safe Haven, The Best Of Me and now The Longest Ride. Another – The Choice – is scheduled for 2016. Given Sparks has published seventeen novels to date, there are still another six to adapt, so we’re set until at least 2022 even if he never writes another word.

The author Nicholas Sparks Credit: Rex Features

How has Sparks, a former pharmaceutical salesman, achieved all this? Put simply, he has a formula and he sticks to it. To mark the release of The Longest Ride this week, the 10th Sparks adaptation to hit cinemas in the UK, we look at just how he does it:

Don’t call it a romance

Perhaps because the genre is associated with lady writers who wear a lot of pink, the martial-arts practicing Sparks refuses to countenance any description of his love stories as “romance”. In an interview with USA Today about The Last Song, starring Miley Cyrus, he said, “If you look for me, I'm in the fiction section. Romance has its own section. I don't write romance novels. Love stories — it's a very different genre. I would be rejected if I submitted any of my novels as romance novels."

Miley Cyrus and Liam Hemsworth in The Last Song Credit: Rex

Of A Walk To Remember, he said in 2002, “It’s not a romance novel. This is not a dreamy fantasy. It is about real love on a number of levels.”

Trumpet your literary history

Sparks writes 2,000 words a day, three or four days a week, for four or five months at a time on each of his novels. He’s managed roughly one book a year since 1996. And the author sees himself as part of a grand tradition. “I write in a genre that was not defined by me. The examples were not set out by me. They were set out 2,000 years ago by Aeschylus, Sophocles and Euripides. They were called the Greek tragedies. These are love stories. They went from (Greek tragedies), to Shakespeare's Romeo and Juliet, then Jane Austen did it, put a new human twist on it. Hemingway did it with A Farewell to Arms."

All that said, Sparks believes in adhering closely to his formula. "I could, theoretically, do a novel set in the 1800s,” he told GQ.  “But the last thing I want to do is a novel that not a lot of people may read, because it's not what they expect. I don't want to disappoint them if they bought my book on good faith, expecting one thing, only to discover I delivered something entirely different. Maybe it's just that I wasn't wealthy growing up, but when I ask people to take money they've earned working and support my career, I want to give them their money's worth."

Find the conflict

The tough part, says Sparks, is to find “the primary conflict” that will keep his characters apart despite their instant attraction and evident compatibility. In Dear John, it’s 9/11 and the hero’s determination to go fight in Afghanistan. In Nights In Rodanthe, it’s the hero’s immediate need to go reconnect with his son in South America.

If all else fails, it will emerge that one of our central couple is rich and has a snooty family who disapproves of the other’s humble background: this trope crops up in The Notebook, Dear John, The Best Of Me, The Last Song, A Walk To Remember and The Lucky One. Whatever stands in their way, no one will curse at any point.

Find the characters, then let love tear them apart

This is easy. At some point in the last 80 years or so, our straight, white heroes meet in a beautiful town on the eastern North Carolina coast. She will be gorgeous, but humble, and unlucky in love. He will be stoic, a man of few words who has a capacity for violence that he keeps leashed. He will look great in jeans. But something stands in the way of the spark of attraction between them. At least one will have a tragedy in their past, like a dead spouse or an undeserved prison sentence or a family illness (Safe Haven, The Best Of Me, The Last Song).

There are those thorny class issues, because one of them almost certainly lives in a beautiful antebellum mansion and the other comes from the wrong side of the tracks. Occasionally, there will be a War, and our manly hero will have to go away and fight (Dear John, The Notebook, The Longest Ride). And if all else fails, the heroic pair’s own high ideals will separate them and demand that one of them sacrifice his or her happiness to the greater good, at least temporarily (Dear John, Nights In Rodanthe).

Scott Eastwood and Britt Robertson in The Longest Ride Credit: Twentieth Century Fox Film Corporation/Michael Tackett

The young couple will almost certainly have a wise old mentor who will help them work through their issues. If you’re very lucky, this character will be played by Paul Newman, as in Message In A Bottle. If less lucky, this role will be taken by Safe Haven’s Cobie Smulders, playing the ghost of the male lead’s tragically deceased wife, who befriends the fugitive heroine.

Kill your darlings

After someone dies at the end – and at least one person always does – the film’s survivors will learn a bittersweet lesson about life and love and emerge with a sense of quietly tragic happiness. Occasionally one of the central couple will die, just to keep you on your toes, but more often it’s a family member. You can usually spot the sacrificial lamb because they will be the one spouting the most obnoxious cod-philosophy about savouring life and following your heart. The soon-to-be-dead, you see, are very wise and in touch with the universe. Or as Sparks puts it, “Faith, forgiveness, family – if you get it just right, these are themes that touch viewers, because they recognise them in their own lives.”

Find 'em young

To Sparks’ credit, or perhaps Hollywood’s shame, his films tend to attract real talent despite having little in the way of genuine character. A whole string of handsome leading men have peopled his films, hoping for that Ryan Gosling bump to heartthrob status. Sparks helped the careers of Channing Tatum, Liam Hemsworth, Zac Efron, Josh Duhamel, Luke Bracey (soon to star in the Point Break remake) and now Scott Eastwood in The Longest Ride.

Ryan Gosling and Rachel McAdams in The Notebook Credit: Melissa Moseley

It’s fair to say that the female leads have probably seen less of a career bump as a result, but it also didn’t hurt the prospects of Julianne Hough, Amanda Seyfried, Taylor Schilling and now Britt Robertson. And at least the quality of the supporting casts remains high: the likes of Richard Jenkins, Blythe Danner, Alan Alda, Viola Davis and Scott Glenn are to be found adding some heft to all the romantic angst.

NEVER change the poster

There is one aspect of the Sparks formula that is absolute. The posters for all these movies must involve a man with his hand on a woman’s face, or as one online wag titled them, “White people almost kissing” (see main pic, above). On no account should you deviate from this rule, which has been achieved following extensive testing.