Nicholas Sparks has discovered a literary path that leads directly to the tear duct.

Six of Sparks’ novels have been converted into hankie-wringing cinematic melodramas, including “The Notebook,” “Message in a Bottle,” “A Walk to Remember,” “Nights in Rodanthe” and the upcoming “The Last Song.”

The latest Sparks adaptation is “Dear John,” brought to the big screen by a director who knows a thing or two about the weeper genre, Lasse Halstrom (“My Life as a Dog,” “What’s Eating Gilbert Grape,” “Chocolat”).

Amanda Seyfried (“Mamma Mia!”) stars as Savannah, a pretty UNC-Chapel Hill student from an affluent Southern family. She and John (Channing Tatum from “G.I. Joe: The Rise of Cobra”) ‘meet cute’ when the Army Special Forces soldier risks his life by diving into the Atlantic to rescue Savannah’s fallen purse.

Can amour be far behind?

Over a two-week period, their flirtation blossoms into love. But in the Sparks tradition, these two encounter more than their share of challenging complications.

Sparks really stacks the deck against this budding romance, saddling them with difficulties that rival those of Romeo and Juliet.

For John and Savannah, it seems that the world has conspired against them. Autism, cancer, 9/11, war and other forces beyond their control intrude upon and impede their romance.

The cast includes some very talented supporting players, especially the terrific Richard Jenkins (“The Visitor”) as John’s father, who may or may not be suffering from an emotional disorder.

The criminally underused and misused actor Henry Thomas (“Gangs of New York”) also makes an impression as Tim, Savannah’s friend who spends most of his time caring for his autistic son.

As in many movie adaptations, however, there isn’t enough time to establish the novel’s supporting characters. The leads are then burdened with making their coupling as compelling as possible.

While Seyfried and Tatum are likable and attractive actors, they don’t have a lot of charisma or establish much chemistry between them. For a story that is utterly anchored in this relationship, it’s a substantial flaw.

Hallstrom and screenwriter Jamie Linden (“We Are Marshall”) manipulate our emotions in the potent Sparks tradition. Some viewers will, no doubt, feel like they’re being jerked around.

But for those who don’t mind sentimental calculations…or for those who just enjoy a good cry, “Dear John” might just fill the bill.

For everyone else, a tear may appear in the corner of your eye…but you may well resent it. (PG-13) Rating: **1/2

* Avoid at all costs
** Only if you're bored
*** Good movie
**** Well worth your time
***** Be sure to see it