Here is the fourth screen adaptation of Choderlos de Laclos' Les Liaisons Dangereuses, a novel derided centuries ago as ''a picture of the most odious immorality.'' Director Roger Kumble treats its plot as the framework for a glossy exploitation film; he's less concerned with exploring the souls of cynical libertines than with plumbing the nuances of teenage lesbian tongue-kissing. Phillippe's Valmont and Gellar's Merteuil are bratty Manhattan step-siblings who lay a carnal wager over whether he can waste the chastity of Reese Witherspoon's little miss. Cruel Intentions is odious, sure, but its first hour is so zippily titillating as to make for tasty trash. Viewers eager to gobble more of the same can tune in to the film's TV spin-off, Manchester Prep, this fall. C+