If only it could have taken itself less seriously. If it had the cartoonish atmosphere of, say, “2012,” then “World War Z” would have been a silly, fun popcorn movie.

As it is, it takes itself seriously and is thereby a partly dramatic, partly silly science-fiction piece.

No one who reads much about filmmaking or stars will be surprised to learn that the show is a letdown after its well-publicized rewrites and re-shoots. It’s not a terrible movie; rather, it’s a big-budget disappointment.

Brad Pitt plays Gerry Lane, a former military investigator who lives happily at home with his wife Karin (Mireille Enos) and two girls. He and his family face a zombie invasion head-on while driving through Center City, Pa.

Through his military contacts, Gerry arranges the rescue of his family. Afterward, he’s offered a deal: His family will stay safe aboard an aircraft carrier if he will join a team that includes Navy SEALS and a crackerjack epidemiologist to find the origin of the zombie “illness,” if you will.

Gerry ends up aboard a plane headed to South Korea, the first step in a dangerous journey that also takes him to Israel and Wales. He joins troops, scientists and individual soldiers as they flee and/or try to resist the fast-moving zombie menace.

I have nothing against PG-13 films, but the show would have been stronger if it had received an “R” rating. This is the first movie helmed by Marc Forster that I can honestly say does not rate very good or excellent. Forster also directed “Quantum of Solace,” “The Kite Runner” and the too-little-seen “Stranger Than Fiction.” Because of the movie’s rating, Forster is forced to cut away during many action scenes, so we can’t see what’s going on because the rating prevents us from doing so.

Pitt, as always, delivers a wonderful performance that will have the audience rooting for him. His character is smart and relies not on his brawn but on his brain to survive and figure out exactly what he’s dealing with.

The silliness factor is just as high as the dramatic pluses, what with a chihuahua running around on a plane during a critical scene and people surviving ghastly wounds with superhuman strength, practically shrugging off injuries that appear critical or fatal.

No one’s career will be dead after this. But it won’t breathe life into anyone’s resume, either.

To read the complete review, go to qctimes.com/goanddo.