(PG) ***

Director: Ben Stiller.

Cast: Ben Stiller, Kristen Wiig, Adam Scott, Sean Penn, Shirley MacLaine, Kathryn Hahn, Patton Oswalt.

FROM Reality Bites to Tropic Thunder, Ben Stiller makes intriguing and varied films whenever he sits down in the director's chair.

But no one probably expected something quite so adventurous as this take on James Thurber's renowned short story, which was famously filmed in the '40s as a Danny Kaye vehicle directed by Norman Z McLeod.

Stiller's version bears as little resemblance to Thurber's story as the McLeod version did - all that remains is the name and the fact that Mitty (played here by Stiller) is a man who "zones out" of his dull life, daydreaming amazing and heroic achievements to make up for the ordinariness of his everyday existence.

In this iteration, Mitty works at Life magazine as clerk in the photography department and is charged with handing over the image for the final cover - a "quintessence"-capturing shot from acclaimed snapper Sean O'Connell (Penn).

But when the negative can't be found, Mitty must finally break out of his work-a-day drudgery and do something noteworthy.

It's an ambitious film from Stiller and its $90 million budget is evident on the screen in some stunning set-pieces straight out of Mitty's imagination, such as a flying leap into an exploding building and a rolling streetfight through New York traffic.

This ambition and excitement keep the enjoyment level rolling along through the dull patches. The movie comes crashing back to earth each time Mitty returns to reality, which is obviously the plan, but even when Mitty finally takes off on his big adventure, the film struggles to keep a consistent pace or tone.

While initially touted as awards bait, The Secret Life Of Walter Mitty doesn't quite get to that level. It aims to be profound but its central message and theme - that Mitty needs to get a life - is hammered home with all the subtlety of a helicopter to the face. Mitty works at Life, the magazine's "meaning of life" motto is trotted out about a dozen times ... yeah, we get it.

But you still have to admire the film. It's fun and inventive, and Stiller tries to tap into his inner Michel Gondry, with inventive visuals that bring the imaginary world crashing into the real one, even if it lacks the high levels of quirk found in Gondry films.

It's also one of the better Stiller performances we've seen to date, while Scott is wonderfully obnoxious as the manager in charge of shutting down Life magazine, Oswalt is funny as an eHarmony technician, and Penn is nicely restrained as rogue photographer O'Connell.

The plot itself is both frustrating and rewarding. I'm terrible at predicting twists, but a major plot point about the missing negative almost had me screaming at the screen for an hour. Despite this, the film still managed to resolve in a satisfactory manner.

It's this kind of up-and-down nature that sums up The Secret Life Of Walter Mitty. As adventurous as it is, it still feels very safe. As charming as it is, it's also very frustrating. And as much as it has a lot of warmth and heart to it, it comes off as obvious and a bit superficial.

Thankfully it's fun and predominantly enjoyable though, making it definitely worth a look. Stiller has aimed high, and even if he hasn't made it to the top, the view is still pretty good from where he ended up.