“Diary of a Wimpy Kid: Rodrick Rules”

The huge popularity of the “Diary of a Wimpy Kid” books can be traced to one simple fact: They ring true.

Their underachieving preteen hero Greg Heffley – whose diaries they purport to be – has no reason to lie. He’s writing (and drawing stick-figure-like illustrations) in a private journal, after all. As a result, the picture they paint of the modern middle-schooler feels very real. At times, Greg can be an inconsiderate, lazy, ungenerous and resentful screw-up, though he’s basically a good, and mordantly observant, kid. Flip through a few pages and just count the number of times you see the words “to be honest with you” and “the truth is.” He’s a flawed and funny Holden Caulfield Jr., a bumbler with backbone.

If only the new movie based on the second book in the series, “Diary of a Wimpy Kid: Rodrick Rules,” were as candid, or as hilarious.

Oddly, the latest live-action adaptation of author and illustrator Jeff Kinney’s bare-bones novel/comic strip – directed by former animator David Bowers from a script by Gabe Sachs and Jeff Judah – comes across as more cartoonish and less sincere than the original. One of the greatest offenders is Steve Zahn. The actor, who plays Greg’s dim-bulb dad, Frank, and who is at his best when deadpan, is guilty here of almost criminally pop-eyed mugging. As the titular Rodrick, Greg’s teenage brother and chief tormentor, Devon Bostick verges on the sadistic.

More heartfelt and low key is the performance of Zachary Gordon as the now seventh-grade Greg. Gordon manages to capture Greg’s put-upon likability, standing out in a cast of mostly lackluster juvenile supporting actors, whose characters pale in comparison to their literary antecedents.

The problem doesn’t really lie in the acting but in the writing. There’s too much effort expended on making the kids cute and cuddly, instead of plausible. As my 11-year-old son (and expert focus group) put it, you end up feeling sorry for Greg, when you should be laughing at him.

Not that there aren’t some amusing moments. If your sense of humor is still fixated on poop stains, incontinent birds, flatulence, underwear and diapers, you’ll have, if not a field day, at least a few giggles.

Unlike the book, whose focus, like an actual diary, is somewhat scattershot, “Rodrick Rules” centers on Greg’s infatuation with Holly Hills (Peyton List), a pretty girl who’s clearly out of his league, and his ongoing antagonistic relationship with Rodrick. That’s okay. It makes for a more cinematic – if conventional – narrative, and this is, after all, a movie.

You can’t fault the filmmakers for reshaping a diary into a cohesive film. You can, however, fault them for taking one of the great antiheroes in preteen literature and turning him into, well, an even wimpier kid.