BONG WATER by Michael Hornburg (Grove Press: $11; 189 pp.). Hornburg’s promising, often comic first novel chronicles the misadventures of a wannabe filmmaker in Portland and his twentysomething friends. Despite political rhetoric to the contrary, these alienated members of the “grungeoisie” know that the glow over America is a sunset, not a sunrise. Although they dabble in the arts, they don’t expect financial or aesthetic success; their expectations are limited to drugs and bed partners. But even lust barely stirs them: “Sex is so ‘80s.” Hornburg suggests that the anthem of Generation X is not cry of a rage or even despair, but a disillusioned whimper.