Low-key offbeat mood movies like The Rum Diary have always been tough sells, even if they’re relatively assured and “well made” as far as that goes. The odds are that half the critics are going to take a dump on them because they aren’t dramatic or wacko or plotty enough. But dry, rambling, mild-mannered half-comedies are okay in my book, and I was surprised to discover earlier this week that this long-delayed Bruce Robinson-Johnny Depp film is far from a burn.

Either you let it in or you don’t. It is what it is, and it ain’t half bad.

“No, wait…that’s not what we want!,” says the public. “We want madness, cojones or some kind of extremity. We want deep-river emotion or major nutso insanity or…whatever, something weird or new or jaw-dropping or pants-dropping.” Well, Rum Diary isn’t that. Which is why it’ll be gone from theatres fairly quickly.

If you’ve followed the tortured history of this film, shot in early ’09 and then found wanting by distributors and set out on a path of unloved loneliness, you would naturally expect it to play like some kind of calamity. That’s what I was mostly expecting. And when it turned out to be what it is, I felt mildly pleased. It’s an in-and-outer, mostly an inner, and reasonably adult and thoughtful and measured. It works according to its own modest design.

I for one am sick of the rules of doper or absurdist or extreme-misfortune-happening-to-idiots formulas, and I felt mildly amused and half-charmed by this dry, no-big-deal thing. I loved that it kept its laid-back cool and didn’t force a comedic agenda into the folds of its slight narrative. And the fact that the story, set in 1960 Puerto Rico, feels like it’s actually happening in 1960 and not a 2011 version of same.

Everyone knows the gist of the Hunter S. Thompson book by now. Depp’s Paul Kemp is Thompson as soft clay, uncertain of mission, a pre-60s guy in the sense that the ’60s began with the Kennedy assassination, pre-Hells Angels book, pre-Fear and Loathing, pre-Woody Creek, pre-almost everything.

Rum Diary is basically a Hunter S. Thompson origin saga — i.e., how the late gonzo writer came to find his soul and his voice at the beginning of his career.

Kemp arrives in San Juan to work for a failing daily newspaper, and becomes chummy with the paper’s boozy, slightly fungusy photographer (Michael Rispoli) and some kind of slimy, greasy newsroom oddball (Giovanni Ribisi) who hangs around and drinks. He meets Puerto Rico’s greedy capitalist cabal (led by Aaron Eckhart‘s “Sanderson’) and stupidly falls then falls in love with Chenault, Sanderson’s hottie-blondie girlfriend (Amber Heard).

What happens? Sanderson hires Kemp to write some kind of real-estate brochure that will presumably generate investor interest, but Kemp barely types a word before falling in love with Chenault, which naturally leads to eventual conflict with his employer. This and that happens (a lot of beautiful Puerto Rican scenery) including too much drinking, the watching of one of the Kennedy-Nixon debate on a TV belonging to a neighbor, and the taking of some kind of hallucinogen via eyedrops. But the basic offshoot is that Kemp realizes he despises slick opportunistic hustlers like Sanderson and will henceforth devote his life to giving them as little comfort and as much anguish as possible.

It goes without saying that it’s a pleasure to see Depp not wearing mascara or a pirate hat and being somewhat naturalistic, and at the same time inhabiting the same Hunter Thompson he played in Terry Gillliam‘s Fear and Loathing in Las Vegas (an unfulfilling film that was nowhere near as good as the book) only this time with hair.

I should have written this two or three or four days ago (I saw Rum Diary last Tuesday night) but it wouldn’t come.