GETTING USED TO DYING by Zhang Xianliang (Harper Collins: $19.95; 293 pp.) . Given the current reality of life in China, what is rational? Given the politics of the West, what is absurd? Zhang describes life under dictatorship and how it affects the very fiber of one's identity and morality, even one's concept of human existence. All very tragic, defeatist, depressing. But is the contrast a liberation? Zhang zigzags from Beijing to burlesque, from labor camp to literary convention; his writing is as frustrated by capitalist decadence as it is by Communist brutality. Still, the writer condemned by oppression has an advantage over the writer in a free society, because he is blatantly brave and his concerns are as basic as life itself. The author chooses his motherland instead of freedom in the West, but he also chooses to write, fully aware of the danger of doing so. These choices give incredible power to this novel about politics, death and sexuality.