By Greg Vellante
Correspondent

“Dear John” is a romantic weepie that succeeds most in executing what it adapts. Based on yet another novel by Nicholas Sparks (the unofficial king of the genre), the movie will be interpreted exactly as the book was. There’s a love story, and there’s drama, and everything that happens in between is simply filler.

John (Channing Tatum) and Savannah (Amanda Seyfried) fall in love during a brief two weeks while John is home on leave from the military and Savannah on vacation from school. He heads off to war, she to school, and they remain in constant contact through sweetly detailed letters sent back and forth during their time apart.

While watching these two actors create rather convincing chemistry on screen, it’s hard not to fall for the indisputable enchantment of it all. I’ve always had an appreciation for Tatum, a big lug with previous roles in films like “Stop Loss.” “Dear John” showcases his sensitive side, with Seyfried providing just as much allure.

The letter montages are equally authentic in showing how the written word can work miracles in maintaining a soldier’s morale. I found the scenes reminiscent of the sublime 1987 documentary “Dear America: Letters Home from Vietnam,” in which actual letters from soldiers to loved ones were read by various celebrity voices.

If the story hadn’t decided to take a complete left turn approximately halfway through the film, I wouldn’t be reluctant to recommend “Dear John” as a movie worth seeing.

Unfortunately, the movie does decide to steer its way into unnecessary dramatic plot points, and by the final credits, it has completely driven itself off the road.

Aside from the love story mixed with war, there’s an interesting side plot involving John’s father, played by the always-brilliant Richard Jenkins. Through it’s never fully stated, John’s father is believed to have a mild form of autism, causing him to be odd, unsocial and occasionally unstable. Jenkins gives a great performance — at once tragic and heartfelt — among the movie’s typical romantic fare.

Unfortunately, when the story dives into even more side plots, involving the post-Sept. 11 war, death and cancer, it loses touch with the original love story it set out to present.

I enjoyed the touching portrayal of a long-distance relationship and its ability to persevere, and also how the simple act of putting a pen to paper and writing how you feel can remedy that void almost instantly.

I didn’t enjoy yet another manipulative tale trying to gain access to the water release valve in my tear ducts. Especially when, in doing so, “Dear John” sacrifices its authenticity, the one thing that made it so worthwhile in the first place.