by Knopf, $12.95. Mr. Wharton’s novel describes the misadventures of a halfdozen American soldiers posted to an abandoned chateau in the Ardennes forest at Christmastime in 1944. Four of the group, Including the sergeant narrator, are still in their teens. All of them are inappropriately intelligent, sent to the front by snafu. They have neither taste nor talent for warfare, and their attempts to introduce a few civilized arrangements into their situation produce results that are semi-fantastic, grimly funny, and ultimately horrifying..