"The Rum Diary," based on Hunter S. Thompson's semiautobiographical novel, gives Johnny Depp the opportunity to play another type of Caribbean drunk. If this makes you anticipate a rollicking farce, take a moment and reset your expectations. Set in Puerto Rico in 1960, it's the story of a young man's journey, physically and spiritually, into very unfamiliar terrain.

Paul Kemp (Depp) takes a job at the failing English-language San Juan Star newspaper as a stopover on his way to becoming a novelist. The story takes Paul through situations that are in turn dramatic, romantic, comical, violent -- and above all uneven.

Paul is the pre-political, pre-hallucinogens Thompson, an unformed writer who finds himself while exploring the extreme southern frontier of America. This is Depp's second whack at the character. He offered an idiosyncratic impersonation of burned-out, late-career Thompson in Terry Gilliam's psychedelic "Fear and Loathing in Las Vegas" (Depp also narrated Alex Gibney's documentary "Gonzo"). The films are entirely unalike but share a common problem. Thompson, a thrill-ride writer, makes a prosaic leading man.

Dialing back the decades, Depp, now 48, does a convincing job as a naive newbie journalist.

The character is closer to "The Great Gatsby's" Nick Carraway than Capt. Jack Sparrow. Stranded on an island that is beautiful, cruel and chaotic, Paul has his eyes opened to injustices more easily ignored on the mainland. The newcomer catches the attention of shrewd operator Sanderson (Aaron Eckhart), who recruits him to publicize a shady development deal. Paul is drawn to Sanderson's opulent lifestyle (yachts, sports cars, even a bejeweled tortoise) and eye-candy mistress (Amber Heard). He's even more repelled by Sanderson's racism and greed: The swaggering entrepreneur threatens to shoot poor islanders who venture too close to his private beach.

Paul is transformed from thoughtless alcoholic to irate muckraker. But his paper won't print his exposés. The cynical editor (Richard Jenkins) fears upsetting the "vividly average" readership, and confines Paul to writing puff about tourist attractions. What's a muckraker to do?

Kemp drifts from one misadventure to the next with no clear purpose, and so does the film. Writer/director Bruce Robinson, who created the sublime alcoholism tragicomedy "Withnail & I," and wrote the screenplay for "The Killing Fields," captures vivid contrasts between the island's lush scenery and grinding poverty. There's a gallery of flavorful supporting characters, including Giovanni Ribisi as a drug-ravaged ex-writer who foreshadows Thompson's final years. What's missing is a sense of dramatic urgency. The film is a colorful travelogue unsure of where it's going.