''My hobby is making a billion dollars. After I have it my hobby will be spending it,'' the fallible hero of Smiley's thick field study of a novel announces, and he's only half kidding. Good Faith surveys deal-greedy, deregulated 1980s America through the increasingly risky business and romantic transactions of a divorced suburban Realtor and pronounces the whole decade a scam dressed up as an irresistible offer. But since Smiley clearly has indictment on her mind from the get-go, the undifferentiated characters -- all of them suspiciously articulate -- begin to feel more like arguments on legs than real people. (Even a couple of racy sex scenes have an educational subtext.) Indeed, lessons spill out of the mouths of these garrulous Americans the way other folks say ''howdy.''