Cleveland, 1987: Popular late-night shock jock Barry Champlain (Liev Schreiber) spins ratings gold from call-ins. His shtick: confrontational honesty. His MO: insults. Transvestite? Barry thinks you're a cliché. Pregnant? You're a slut. He's not casually cruel: In Barry's bloated mind, folks listen because ''this country's rotten...and needs a loudmouth to tell it like it is.'' Talk Radio — set entirely during Barry's show and featuring a string of disturbed callers (and impressive chain-smoking by Schreiber) — depicts his fretful realization that listeners just like to hear people painfully humiliated, and that he's essential to the cultural decline that frightens him. Heady stuff — especially considering that as an audience watching Barry's breakdown, we're implicated in the ghoulish voyeurism Talk Radio rails against. Yet Schreiber, writer Eric Bogosian, and director Robert Falls overlook that for this smart, mind-bending play to work, Barry must be captivating. We don't have to like him — though Talk Radio seems to want us to, subjecting us to useless monologues by his sidekick (Barry is a tormented genius!), girlfriend (Barry is a lost puppy!), and boss (Barry is a media puppet!). We have to enjoy him to buy that people would adore his sick broadcast and to feel justifiably smacked at the play's end. But with all his dated ranting (''How about...I get David Berkowitz, Bernhard Goetz, and John Hinckley on?'') and Schreiber's overacting (try telling if he's sad or being bitten), that's one tall order. B-