One of the half-truths long associated with American literature is the charge that our important writers produce their best work early, then settle for repeating themselves, book after book, frustrating and disappointing their admirers. Many readers of contemporary fiction would probably agree that that's the case with Kurt Vonnegut. A fantasist and satirist whose inventive early novels (such as ''Mother Night'' and ''Cat's Cradle'') seemed brilliantly sui generis, he is now become a beloved institution whose recent productions parade forth wan, cute expressions of plucky humanism overcome by despair.
''Deadeye Dick'' is weakened by the coy rhetorical trickiness which seems almost re-flexive with Vonnegut - but the good news is that it offers a compensatory sufficiency of clever and funny inventions. It's his best book since (his last really good one) ''Slaughterhouse-Five'' (1969).
It's the story of Rudy Waltz, scion of a wealthy pharmaceutical-company family of Midland, Ohio; of how he became an accidental double murderer at age 12, firing a gun out of an upstairs window, hitting and killing a pregnant housewife, vacuuming - on Mother's Day; of his later life as failed playwright and ''defective human being''; of the also unintentional ''depopulation'' of Midland City by a neutron bomb - and, now that I think of it, actually quite a lot more.
The story, told by himself, comes to us in Rudy's 50th year from the hotel he runs on the island of Haiti, together with his brother Felix, a defrocked network television executive. It is told in succinctly simple prose only occasionally made turgid by Vonnegut's patented homily-refrains. ''Watch out for life'' is the main one. The formal narrative, such as it is, is subjected to frequent interruptions - recipes and outbursts of ''scat singing,'' for example - and even radical quick changes, as when Rudy presents certain key scenes in dramatic form. ''I have this trick,'' he says, ''for dealing with all my worst memories. I insist that they are plays.'' This hybridization nicely expresses what I take to be the novel's primary message: that rationality and purposefulness got the world into the mess it's in now, and we'd all be better off if we practiced simple human kindness.
Of course this is oversimplification - as is the novel's deadpan recording of horrible wrongs unthinkingly perpetrated by people. Many readers won't like this special pleading, or the book's overload of sentimentalism, which includes quests for ''Shangri-La'' and gestures of solidarity with the disadvantaged. Nor will they like the wheezy rhetoric (''The planet itself . . . (is) breaking down''). Vonnegut has taken us down this road too many times already.
Fortunately, the novel's preachy humanism seldom interferes with its bizarre comic logic; it's as if these components run on separate, parallel tracks. Consider the case of Rudy's father, Otto, that ''dangerous nincompoop'' who once bought a painting in Vienna from fellow art student Adolf Hitler - and thereafter became a self-willed artist and man of action, an avid gun collector, and inevitably the indirect cause of the tragedy that ruined his family's name.
Both a ridiculous and tragic figure, Otto Waltz exerts an oddly compelling claim on our sympathies. So does this novel: We feel Vonnegut's honest moral passion pulsing beneath the cuteness and thinness that compromise it as art. ''Deadeye Dick'' can hardly be called a complete recovery of form, but it does offer vividly convincing proof of Vonnegut's unique, probably undiminishable originality and charm. Even when he's only half-trying, he remains one of our most engaging writers.