A CRUEL MADNESS. By Colin Thubron. Atlantic Monthly Press. 168 pp. $13.95.

COLIN THUBRON is an Englishman who has written a number of travel books about the Eastern Mediterranean, and created in A Cruel Madness an intriguing and sometimes rather moving novel about insanity and love, illusion and reality.

His hero is a feckless fellow named Daniel Pashley, an English teacher trapped in a small, depressing boys school in Wales. (Ever since Evelyn Waugh's Decline and Fall, British authors seem to consign their wetter protagonists to depressing boys' schools in Wales. Why?) Despite a certain shy charm, decent looks, and a real way with words, Daniel's love life is only another British depressed area until he meets a local doctor named Sophia, who while treating a torn ligament in his leg, captures his heart. Though Sophia seems engaged either with, or perhaps to, Another Guy, shy Daniel gathers the courage to invite her to lunch, where he impresses, touches, and secretly pleases her. Sophia gently encourages him, and soon enough Daniel is making quite spectacular headway. It's love. Daniel's dreary sexless days are over -- until suddenly, without the slightest effort to provide any kind of plausible explanation, Sophia informs Daniel that she is leaving town and dumping without reprieve both Daniel and his sometime rival. Period. So long, Daniel, and tough luck.

Daniel creeps back to the boys' school and his shy, crushed-out bachelor's days. Years pass. Daniel the unloved (with his unfailing sense of where to look for fun) volunteers to teach English in a local mental hospital. There in the awful wards his tragedy is completed when he comes upon a mute, ruined, devastated schizophrenic who is none other than his lost Sophia.

A sad story. Yet as the novel unfolds, we grasp that it happens not to be the real story. In truth, Daniel is no volunteer. He is a patient in the hospital. The lost love haunting the dour warren of the hospital is his hallucination. Indeed, his original affair with Sophia, perhaps even the dreary teaching job, may likewise be delusions. He's been hospitalized a long time, though he intermittently recognizes the delusory nature of the story he's concocted to explain his wretched life. When not ransacking the grounds for the elusive Sophia, he's one of the more together guys in the common room. At last, the beloved apparition appears to reject him one final time. His last illusion dead, Daniel deteriorates into the inert despondency of the chronic ward, a lost though uncommonly articulate, soul.

Another sad, though not entirely convincing, story. I never quite bought Daniel as a mental patient: his disturbance (not to mention Sophia's ghostly role) struck me as a tad literary and contrived. Both this madness, and this Sophia (wisdom?) seem more likely metaphorical, indeed allegorical. It must be added that Thubron buttresses this impression with a wide range of the more familiar shibboleths of the British genteel-left. There is a noble coal miner. The leader of the men's ward is a fat loathsome money-grubbing Colonel Blimp. Every staff member is hateful, every doctor ineffectual. Religion is an active theme, treated with weary insulting disdain until provided with an Eastern -- "Buddhistic" -- slant, whereupon it becomes vaguely beautiful. Sophia (invented or no) duly complains about the sexism marring her medical career. Being a woman, Sophia is good. Daniel, even though he is a man and without the good fortune to be a noble coal miner, is redeemed from being bad by being pathetic.

THE THEME underlying these leftish cliches is how one man is destroyed in a struggle between illusion and reality. This is the part of the novel -- Daniel's decline -- that I found touching and at times truly moving. My problem raises another issue: what, and how, the imagination believes. Was Daniel once jilted by a real Sophia, or is she entirely a figment? We are never told. I find this odd. The reader -- this reader, anyway -- can neither judge nor care about a triumph of illusion over a reality that is unknown. The moment I caught on to Thubron's plan never to let me in on his little secret about Sophia, I confess that my entire interest in the woman dropped down dead and never revived.

British storytelling just at the moment seems in the midst of a mini-vogue for mystification achieved through the absurdly simple device of omitting major pieces of information from an otherwise perfectly ordinary story. (Another excellent recent example is David Hare's film Wetherby, with Vanessa Redgrave). This is what happens in A Cruel Madness, and I for one find it a cheap trick, an effort to make a story more portentous, merely because it is more perplexi, than it has any right to be. The surface of Thubron's narrative is elegant and quite unaffected, but if I had to guess the source of this exasperating device it would be the so-called post-modernism of the '70s, and its mistrust of stories as such. Stories, in this view, were vulgar, or naive, or unoriginal, or insufficiently reflexive. Stories were mystifications, part and parcel of the cultural thralldom, the acculturated lie within us all. For sundry ideological reasons, the commentators would have preferred stories banished altogether from fiction, but if it absolutely had to tell them, it might at least have the decency to fragment and undermine them at every opportunity.

Daniel's deluded love strikes me as linked to such ideas. His is the self-enslaved voice of the storyteller, pathetically trying to compensate for the general bleakness of things with its lie. But his lie -- his story -- is not made either more interesting or honest merely by being half-told. Nor is artistic self- awareness enhanced merely because the imagination, ceasing to credit, ceases to care.

But it may be that I have catagorized Thubron unfairly. He is certainly not one of the puritanical Savonarolas of dissociation intent upon demystifying and demolishing the stories' half-truths about beauty, truth, and love the world carries around in its head. His view is more plangent and compassionate, though no less pessimistic, than that. I can only regret that he did not provide that view with the kind of felt reality that would have amplified it to its full power.