"Thank You For Smoking" is a pleasant surprise in many ways: one is that it has an unexpectedly witty and wicked script that's not afraid of irony, and how rare is that. Another is that director Jason Reitman (Ivan Reitman's 29-year-old son making his feature debut) is sophisticated enough to let underplayed and understated moments generate the kind of power that doesn't need to beat us over the head. And since young Mr. Reitman also wrote the film (from Christopher Buckley's novel) we should welcome an exciting and sophisticated new talent.

There's more as well: Aaron Eckhart, who's always struggled to make an impression in his roles, gives the performance of his career as tobacco lobbyist Nick Naylor, always on hand to turn anti-smoking arguments on their heads to make a point. It isn't mentioned in the film but Nick follows Sun Tzu's dictum about war: if you can't win on the battlefield (smoking kills a million a year), move the battlefield (a 15-year-old boy smoker is dying of cancer on the Joan Lunden television show; Nick points out that it's in Big Tobacco's interest to keep him alive and smoking; it's the opposition that wants to kill him to make a martyr).

But what's so attractive is that the film isn't about the ins and outs of Nick's shenanigans; it's about Nick and his relationship with his ten-year-old son Joey (Cameron Bright), and about his membership in a triumvirate that calls itself the MOD Squad, for Merchants Of Death. It consists of Nick, plus a lobbyist for the gun industry, and a lobbyist for the alcohol industry. They share weekly lunches and compare notes. Nick is the winner because his product kills more people than theirs do.

In the course of the film Nick goes from being the go-to guy for Big Tobacco to, well, something else. Along the way he's sent out to Hollywood to persuade top agent Jeff Megall (Rob Lowe) to feature cigarettes in his films; smokers in space seems to be the big high-concept idea. He also visits the original Marlboro Man (Sam Elliott) with a briefcase full of cash because the MM has just been diagnosed with terminal lung cancer. The money is a gift, of course, with no strings attached, but if he takes the money maybe he'll not be so anxious to speak out against cigarettes.

But what makes all of this work - brilliantly - is that Nick takes Joey with him; everything we see and hear is reflected in Joey's reactions to what his dad is doing. Not that we cringe; this film is a comedy, and it stays fun and delicious without straying into parody. It doesn't demean itself by taking itself seriously, and yet everyone is human, perceptive, and wonderfully normal. Reitman's achievement is to let them be and simply trust them and his script to carry us with them.

"Thank You For Smoking" was obviously made without A-list stars, and is the better for it; big names might have skewed it into being a kind of vehicle. It probably flew under the studio's radar until it was finished, which is all the better for us.