||Go ahead and cry. You know you want to. Why else would you read a book by -- or, in keeping with our purposes here, see a movie based on a book by -- Nicholas Sparks?...Dear John, the latest attempt to bring his warm, earnest, therapeutic sensibility to the screen, falls in the upper middle range of Sparks film adaptations. If it lacks the epic sweep and extravagant emotionalism of The Notebook -- Oh, Ryan and Rachel! Oh, James and Gena! -- it also is free of the creepy piety and watered-down eros of A Walk to Remember. In the hands of director Lasse Hallstrom, a blue-chip hack with a sure touch even when he's slumming for a paycheck, this story of interrupted passion takes on a ripe, summery glow...A lot of it succeeds. Mr. Tatum, in his movie roles so far -- A Guide to Recognizing Your Saints and Fighting, both directed by Dito Montiel, are the best -- has shown himself to be an actor of narrow range. But his potential is evident, and his magnetism is undeniable. He is shrewd enough to stay within his comfort zone, and able to make the most of his interactions with more nimble performers, like Ms. Seyfried, a resourceful and engaging young actress industriously turning herself into a movie star...Their likability is the movie's greatest strength -- how can you not root for such nice kids to overcome whatever obstacles life throws in their paths? -- and also something of a limitation. John and Savannah are too thinly drawn to sustain a great love story. Mr. Hallstrom and the screenwriter, Jamie Linden, are careful to respect the vague, whispery tones of Mr. Sparks's writing. (They do, however, change the book's ending in a way that both deepens and blunts its impact.)...But a full measure of romantic complication or psychological depth is not what a movie like this -- or the book it comes from -- is for. Dear John carefully distills selected elements of human experience and reduces them to a sweet and digestible syrup. It may not be strong medicine, but it delivers an effective, pleasing dose of pure sentiment and vicarious heartache.