By D.M. Thomas

Viking. 247 pp. $17.95

The first-person narrator of D.M. Thomas's new novel, "Lying Together," is none other than the author himself, Don Thomas, a writer attending an international writers conference in London. There he meets his old friends, the Soviet writers Masha Barash, Sergei Rozanov and Victor Surkov. Each night this foursome withdraws to a room where they improvise fiction, composing a novel by speaking extemporaneously into a tape recorder. The improvisation is an elaborate literary game; its numerous plots, full of Thomas's trademark sexual, political and narrative trickery, twine around one another, creating a shifting counterpoint to the framing story of the misadventures of Thomas and his cronies.

"Lying Together" is the concluding novel of Thomas's "Russian Nights" quintet, a sequence that includes "Ararat," "Swallow," "Sphinx" and "Summit." Each of these books plays changes on the theme of improvisation; Thomas's fictions are composed of an assortment of narrative fragments spliced together in the effort to achieve an overall associative resonance that is more than the sum of its parts. Sexual fantasies, political satire, history writing, literary theory, psychoanalysis, poems, exchanges of letters and borrowed texts are all loosely interlarded to create an atmosphere of heightened ambiguity, in which everything seems to serve as a metaphor for everything else.

Indeed, it would take fairly sophisticated software to chart all the separate narrative strands of any of the quintet's novels, and it is striking that reviewers of Thomas's work, whether delighted or infuriated, tend to skirt the fragmentary substance of the stories told and address instead the formal apparatus of the telling. Thomas's admirers hail him as a master innovator, a genius of juxtaposition, who has created a world in which all realities are fictions and all fictions realities, a fluid continuum without fixed boundaries. His detractors acknowledge this artfulness but tend to feel that it is little more than literary stuntmanship, a virtuoso sleight-of-hand game that leaves one gasping, "So what?"

In the case of "Lying Together," I must side with the detractors. As the rather obvious pun of the title suggests, the twin obsessions of this novel are Thomas's trademark obsessions: fiction and sex. As far as the fictional "lying together" goes, Thomas's game this time out is to mingle himself and other apparently real characters with invented characters and their real or invented stories until it becomes a constant struggle to determine on what level of artifice or actuality a given passage is operating. The effect is very much what I would imagine it would be like to go rubber rafting on M.C. Escher's waterfall: You don't know which end of the flow you're on -- you only know you're not going anywhere.

The novel's sexual content is equally capricious and sophomoric. Each of the book's many fictions sooner or later devolves into a tale of sexual masochism. One narrative fragment consists of the correspondence between an early German sexologist and a servant girl who is possessed by violent masochistic fantasies. Another fragment tells of a Leningrad woman who poses as a blind movie director to seduce her husband and is raped by an intruder. Then there are the stories of Thomas's Russian friends and fellow improvisers, one of whom commences a lesbian affair only to discover that she likes it when her lover beats her, while another is charged with raping a female journalist who, it turns out, really was conspiring with him to drum up publicity.

It would be dreary enough if these stories were merely as unpleasant and gratuitous as they sound. What makes them truly objectionable is that Thomas presents them as dramatic correlatives to his metafictional agenda of asserting the ultimate ambiguity of the distinction between what is real and what is not. Thomas works his narrative smoke and mirrors to assert that what appears to be sexual violence may actually be the fulfillment of the "victim's" masochistic fantasies. As the baffling plot spins unfold, each story is supposed to make you think: Aha, the raped one was raping the rapist as much as she was being raped -- oh, how ambiguous it all is.

But it's not ambiguous at all. One does not have to be any kind of feminist -- a group Thomas loves to poke locker room fun at -- to recognize that there is no value at all in being told that some people enjoy being violated. Most of us do not. Rather than revealing the profound complexity of discerning the truth in a story, Thomas's two-dimensional sexual fantasies reveal the hollowness of his literary games. After five volumes of the "Russian Nights," we remain as convinced as we were before that however confusing reality may be, narrative manipulation and sexual manipulation are two very separate enterprises. Those who are not masochists will find little pleasure in "Lying Together."

The reviewer is a freelance writer living in New York.