Jun. 19, 2003 12:00 AM

The murder mysteries on Monk are never very challenging for anyone paying the least bit of attention - and this from someone who finds the plot twists on Scooby-Doo surprising.

So what? Doesn't matter. Monk is a delight, because what it lacks in plot it more than makes up for in acting - specifically, Tony Shalhoub's work as the title character.

I've often written that James Gandolfini as Tony Soprano is the perfect match of actor and character, the best TV's ever seen. Shalhoub as Monk is right up there as well.

Bitty Schram is also good as Sharona Fleming, the legendary detective's assistant. Monk needs her. His wife's unsolved murder has left him with a severe obsessive-compulsive disorder, as well as a fear of . . . just about everything. It's both hilarious and wrenching to see Monk - unable to work for the police department any longer but often used as a consultant - in action, picking up on the most obscure clues as he struggles to keep even a loose lid on his sanity.

In Friday's second-season première, Monk works as a substitute teacher to solve the mysterious death of an instructor who fell from a clock tower on campus. He spends what seems like hours struggling to write his name on the chalkboard, worrying to get every line just right; you don't know whether to smack him or hug him.

Later, when he sees a picture of his late wife as a teenager on the school tennis team and says, love mixed with unbearable sadness, "There's my girl," there's no debate. Hugs all around.

There's a sweetness to the show that would have allowed it to fit nicely on a TV schedule 30 years ago, yet Monk never seems dated or out of touch. Creator and executive producer David Hoberman says he was aiming for "a show that's so square that it's hip. . . . I guess it is sort of an old-fashioned yarn."

Nothing wrong with that. Everybody Loves Raymond updates old-fashioned sitcoms, and its actors tote around a lot of Emmy hardware.

Last season, ABC repeated Monk episodes after they aired on the USA network, a great idea for USA because it increased the show's visibility and a great idea for ABC because Monk was better than most of its own programs. Hoberman hasn't heard from ABC whether it'll resume the practice.

"To me, it feels like they're waiting for us to debut to see whether it could be of value to them," he says.

Note to ABC: It can be. The season première, with guest star Andrew McCarthy, would make a nice addition to the network's lineup. Then again, Monk would make a nice addition to any network's lineup.