Yann Martel's slip of a book contains just four of his pre-Life of Pi stories, but they pack a powerful punch. In the moving title tale, the narrator, watching a young friend die of AIDS, devises a game whereby they retell the history of the 20th century year by year along with the adventures of the imaginary Roccamatio family. Martel lets the gimmick go on too long, but the sadness that gradually seeps through the cracks of the futile game is all the more excruciating for being so tightly repressed. The more chipper and polished ''Vita Aeterna Mirror Company'' also strikes deep emotional chords with a light touch: Structured as a frothy conversation between an impatient youth and his aggravating, garrulous grandmother, the story shows the young man's understanding and respect for his elder dawning right there on the page. With uncommon dexterity, Martel manages to inject real, poignant feeling into The Facts Behind the Helsinki Roccamatios's cleverly conceived experimental fictions.