AFTER READING several pages of Changelings, I thought: Tom Marshall`s been watching too much Geraldo and Oprah for the last few years, or he`s come under the influence of Shirley MacLaine. Mediums, channellers, reincarnation, child abuse, incest, sundry sexual deviances, and life behind bars are the grist for this novel; not to mention the fact that the two main characters, a brother and sister, are afflicted with multiplepersonality disorder. The hero, Allen, is also Laird, Allie, Lyle, Al, Lou, and Alana (and occasionally a wooden dummy, Lance). His sister, Eleanour, is less fragmented (Ellie, Lenore, Arlen), though she`s also inhabited by the mythological figures Lilith and Isis. Following the structure of the novel is no breeze, either. It`s built along the lines of a double fugue (a note is supplied to explain this term). In a nutshell, Allen and Eleanour go their separate ways in early life, but their thoughts and their varied alternate personae continue to overlap. Will the two eventually come together, in full knowledge of who they are? Therein lies the suspense. Once I got the hang of it (those first pages were especially tough going), however, I must admit I enjoyed Changelings immensely. The structural challenge is resolved brilliantly in a way I won`t disclose. As for the characters: the hero flits in and out of his multitude of roles in an astonishing and convincing fashion - so convincing, in fact, that the poor reader starts to participate in Allen`s unease (I wondered: who am 1, reading this? the dispassionate academic? the envious rival? the impatient father?, etc.). The heroine, amusingly, turns out to be the medium consulted by Mackenzie King, the former prime minister of Canada and the most notorious spiritualist in our history (give it a try, Brian Mulroney, you have nothing to lose). Then again, the novel is full of fine writing of the kind we expect from Marshall-the section on Eleanour`s first visit to her haunted house is splendid. His insight into the way our roles are layered one upon the other, and the difficulty most of us have in knowing who we are is persuasively drawn. When Eleanour says: "I guess ... there really is no self in the ordinary sense. I mean the way a person usually thinks of himself, herself, is just illusion. Or just one possibility among many. One configuration," we can`t help believing her. Certain aspects of Changelings, however, were less pleasing. The attempts to link identity problems with a vaguely mystical world-view will appear facile to more cynical readers, though they may seem charming and holistic to others. Marshall`s penchant for teaching results in too many explanatory passages - on the nature of consciousness, the Jungian anima, recent research on dissociated personality, sex life in prisons, reasons why actors are so screwed up, etc. Even the prefatory pages contain explanations and definitions of terminology. The novel`s dependence upon psychological and sociological jargon and theory forces the reader (this reader, anyway) into extra-literary judgements. I felt, for instance, that the characters were as much victims of the language of their would-be heaters as anything else. But maybe that was one of Tom Marshall`s points in this provocative, readable book.