The chapters in W alternate between a fiction about an imaginary island called W., devoted entirely to sport, and chapters giving an autobiographical account of Perec's childhood during WWII. Both stories are told in a very crisp, matter-of-fact tone, but the contrast between the two is striking. We read about young Perec's shuffling about and hiding and the death of his parents, though not from his own point of view. Meanwhile, it becomes increasingly clear that life on sport-loving W. is a sort of filtered reflection of the concentration camps (it's a bit like Plato's Republic, too). And because the actual details of life on W. are new, the horror and disgust they provoke is fresh. So although the tone throughout is emotionally detached, the two stories operate like a chemical reaction - while each is neutral in isolation, the combination of the two unnerving and horrific.
W is an experimental novel, but it's not cold or empty; the language is very simple and it was a pleasure to read, went very quickly.