(Warning: A couple spoilers about older Nicholas Sparks movies. Also: Test your Sparks knowledge with a quiz at the bottom of this post.)

Bestselling author Nicholas Sparks had an unusually candid response last year when The Hollywood Reporter asked him about the prospects for “Safe Haven,” the latest in his long line of film adaptations of his romance novels.

“I’m sure it’ll do fine at the box office. They all do,” he laughed. “I mean, it’s why they keep making them, right?”

Well, that’s rather cocky — but also 100 percent accurate? Like all his tearjerker films before it, “Safe Haven” indeed did just fine (eventually raking in $70 million) and the Sparks film factory churned steadily along. Now, the author’s latest book-turned-movie, “The Best of Me,” opens in theaters on Friday and looks like the next reliable entry in his unstoppable movie empire.

The Sparks movie adaptations started in 1999 with “Message in a Bottle,” followed in 2002 with “A Walk to Remember” — but the franchise didn’t really pick up steam until the smash success of “The Notebook” (2004). The Ryan Gosling-Rachel McAdams sobfest launched memes before memes really existed and solidified Sparks’s library as a solid box office draw. Five more films followed. Two more are currently in production.

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The reason for the longevity? In short, he’s an evil genius.

No, really, that’s the only explanation. It’s a special talent to create stories so devastatingly sappy the audience is guaranteed to cry yet appealing enough to come back for more. Sparks’s formula plays into the viewing public’s desire for comfortable predictability. . .  with a twist. In each of his works, Sparks reels you in with the ultimate relatable theme — love! — and sprinkles in just enough surprises that no two are ever the same. At this point, seeing a Nicholas Sparks movie is like listening to a remake of an old song: You know all the beats, but it’s just different enough to keep your attention.

The main plot line is always an against-the-odds love story, though the challenges vary: Alzheimer’s (“The Notebook”), war (“Dear John,” “The Lucky One”), cancer (“The Last Song”), family dysfunction (“Best of Me”) and hey, even ghosts (“Safe Haven”). The endings are generally not happy, but who doesn’t love a good cry?

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Fans of Sparks movies take joy in playing Bingo with all the familiar tropes: The dreamlike coastal village with eccentric, well-meaning neighbors. The wealthy, disapproving parents. The handsome widowers, the gorgeous single moms, the adorable kids. And there is always, always kissing in the rain.

There are the obligatory quirky details to distinguish one movie from another (“The Last Song” has its sea turtles and, if we haven’t already mentioned it, “Safe Haven” HAS A GHOST). And Sparks has mixed it up with some stories dealing with teen romance, others with early-20’s love or middle-age relationships.

​Despite the schmaltz, many Hollywood big shots have made the obligatory stop in a Sparks flick — established stars like Richard Gere and Diane Lane in “Nights in Rodanthe,” or young actors on the rise, like Channing Tatum and Amanda Seyfried in “Dear John.” Some have gone on to hook up in real life: McAdams and Gosling after “The Notebook”; Miley Cyrus and Liam Hemsworth during “The Last Song.”

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For any of them, it’s a nice paycheck for work that, as Sparks knows better than anyone, will do exactly what it’s supposed to do — and pave the way for the next Sparks movie to arrive the following year. “The Longest Ride” already has a release date for April 2015 while “The Choice” is cued up for the year after that. Just like clockwork, the Sparks machine is primed to continue.

CHALLENGE: Can you tell the Nicholas Sparks movie apart by the tagline? Take this quiz by The Post’s Caitlin Moore

1

"A story of love lost and found."

Nights in Rodanthe
Message in a Bottle
Safe Haven

2

"It all comes down to who's by your side."

Dear John
The Lucky One
A Walk to Remember

3

"Behind every great love is a great story."


The Best of Me
The Notebook
The Lucky One

4

"It's never too late for a second chance."

Nights in Rodanthe
The Last Song
A Walk to Remember

5

"What would you do with a letter that changed everything?"

The Notebook
Message in a Bottle
Dear John

6

"A story about family, first loves, second chances and the moments in life that lead you back home."

The Last Song
The Best of Me
Safe Haven

7

"From the acclaimed bestselling author of 'The Notebook' and 'Dear John.'"

The Lucky One
Safe Haven
The Best of Me

8

"You know it when you find it."

The Lucky One
Safe Haven
Nights in Rodanthe

9

"You never forget your first love."

The Best of Me
The Notebook
A Walk to Remember

Your score: 0 / 9

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