Sex, tourism, and sex tourism are on the bill in this dirty novel of ideas. Famous for 2000's blowhard novel/cultural critique The Elementary Particles, Houellebecq here lightens up -- as much as that's possible for an existential nihilist. Michel -- a soul-numbed civil servant -- meets comely travel exec Valerie on a tour of Thailand. Not content with a passionate affair, they plot to promote hedonistic trips for globe-trotters (prompting digressions on colonialism, consumerism, and the human beast). Houellebecq's sex scenes are hot and bountiful, his essayistic adventures no worse than tolerable, and the schematic misanthropy of his earlier work has mellowed into an easy, aphoristic sardonicism: ''It is in our relations with other people that we gain a sense of ourselves; it's that, pretty much, that makes relations with other people unbearable.''