Hollywood is notorious for swallowing up the personalities of its directors ? just look how de-fanged Brian De Palma became once when he stopped plundering his cinema-addled psyche and started cranking out effects-driven star vehicles ? so it’s a relief to report that Christopher Nolan (director of last year’s sublime “Memento”) emerges from the $50 million “Insomnia” with his integrity and ambiguity intact.

A remake of the 1997 Norwegian film of the same name, “Insomnia” isn’t as shattering a mind-bender as “Memento,” but it’s an effective and unsettling thriller that definitively establishes Nolan as a major filmmaking talent.

At it’s skeletal core, “Insomnia” is a capable rehash of the cop-identifies-with-the-killer concept minted by “Manhunter” and “Silence of the Lambs” and worn thin by nearly every single serial killer movie made since.

In less competent hands, this material could be “The Bone Collector Goes to Alaska” ? first-time screenwriter Hillary Seitz’s script is intricate and intelligent, but relies a bit too heavily on genre cliches and ham-handed symbolism to make its points ? but Nolan’s assured direction gives even the flimsiest plot machinations an aura of unknown dread.

Al Pacino stars as Will Dormer, a respected Los Angeles cop who is loaned out to Alaskan police to avoid an internal affairs investigation. Dormer and his partner are assigned to investigate the murder of a local teenage girl, but his faculties are impaired by his inability to sleep under the perpetual glare of the northern lights.

Pacino could probably play the grizzled, morally ambiguous cop role in his sleep ? that’s essentially what he’s asked to do here ? so it would be easy to overlook just how good he is in “Insomnia.” While his fellow Method icon Robert De Niro has been mired in lazy self-parody lately, Pacino continues to take mature roles like this one, giving Dormer a cerebral paranoia that can be read all over his worn, exhausted face.

Robin Williams plays Walter Finch, a lonely writer who’s the main suspect in the girl’s killing, and Hilary Swank is the eager rookie who discovers some of Dormer’s darker secrets. The excellent supporting cast also includes Martin Donovan, Maura Tierney, Nicky Katt and Paul Dooley.

The offbeat casting of Williams, who lately appears to be doing penance for years of blockbuster treacle by appearing in a slew of darker roles, works surprisingly well. Williams uses the sad-sack, puddle-faced persona he established in “Awakenings,” “Good Will Hunting,” “Patch Adams” and the like as an insidious mask that slowly peels back to reveal layers of violence and obsession.

It would be impossible to expound on the plot without spoiling the thrills of discovery, most of which come from the clever ways that Nolan and Seitz construct character and subtly unravel their story ? Nolan is that rare filmmaker who trusts and respects his audience.

Incidentally, the director of the original, Norwegian “Insomnia,” Erik Skjoldbgaerg, recently filmed his American debut with the adaptation of Elizabeth Wurtzel’s “Prozac Nation,” due in Jan. 2003.