DORIS LESSING, long acknowledged as one of the

great writers of novels and short stories in our time, has undertaken two ambitious serial novels. This book is the fourth volume in the second series, called Canopus in Argos: Archives, begun in 1979 with Shikasta. Lessing, better known as a realistic writer, now is trying to write what she calls "space fiction," and this new form seems not to serve her best interests.

Part of the central vacuum of this novel is in the narrator, Doeg, previously a happy, delighted poet- singer in a paradisal world on Planet 8. A participant in a world once composed of sun-burnt mirth, Doeg tells us of the glacierization of his planet, of its slow death by snow and ice. But he, considering he is a teller of tales and a singer of songs, has a curiously leaden ear for narration and dialogue as they all turn to ice cubes.

Lessing's earlier series of novels, called Children of Violence (1952-1969), has a central narrator, Martha Quest. The first four of those novels take Martha through her growing up in Africa and the fifth, final volume plunks her down in postwar London, 1950. Though The Four-Gated City (1969) has an apocalyptic ending (we dart forward to 1990 when The Bomb has done us wrong), Martha even there struggles to make sense of her altered life, continues to seek after essential human goodness and truth. And it isn't a smarmy, hokey struggle in her. And Lessing, deftly and surely, creates a splendid panoply of major and minor characters to accompany Martha on her quest. The themes and concerns occupying Lessing come through clearly as she delineates Martha's life. War, racism, individual consciousness, the male-female sex battles, marriage as an institution, chronological versus psychological time, society versus individual will, all of these spring to life and jump right off the page at the reader. And the reader is grateful to watch so informed and skillful a novelist stretch our minds.

But Planet 8 and its companions in the second series are written in a different style, with a different aim. Lessing the prophet is now creating characters, themes, and structures to hang her pet peeves on. Her current narrator, Doeg, doesn't evince any color, vitality, or social consciousness, for he is sunk into gloom, doom, death, and disaster. Lessing does not give him that quality essential to her other main characters: sprightliness of mind, something she has valued very much and made central in most of her earlier fiction.

Even the dialogues between Doeg and Johor, a main figure in this series, do not spark the reader's interest in the way that they ought. Johor has previously been a Superman figure, dashing about the whole universe, tidying up here and there, popping in like a magus to set each little planet on the right philosophical track. But something has apparently gone wrong in Canopus, for Johor, who was supposed to whisk away the Planet Eightians to the paradisal, pre-lapsarian Rohana, can't do it and must let the Eightians know that the marble wall he made them build around their planet to contain the ice is not sufficient. Johor and Doeg have a confrontation in the middle section of the book, but Johor is curiously silent. Instead, Doeg examines life as he knows it and the following passage reveals the level of sophistication of his thought.

"I have often wondered, when I looked at the tiny oscillations and pulsations that compose us, where, then, are our thoughts, Johor? Where, what we feel? For it is not possible that these are not matter, just as we are. In a universe that is all gradations of matter, from gross to fine to finer, so that we end up with everything we are composed of in a lattice, a grid, a mesh, a mist, where particles or movements so small we cannot observe them are held in a strict and accurate web, that is nevertheless nonexistent to the eyes we use for ordinary living--in this system of fine and finer, where then is the substance of a thought?"

Lessing, an autodidact, is not equipped to answer this last question. As a consequence, the figure standing for her, Johor the Outsider, comes to resemble an Old Testament Jehovah here, not a redemptive, New Testament Jesus Christ. And the confrontation between Johor and Doeg has all the liveliness of a Sunday School tract for tots.

The didactic nature of Planet 8 has behind it the whiff of Presbyterian or Lutheran rejection of the flesh. That aspect is, of course, at odds with her creation of the Eightians as a Jungian collective unconscious, where she again examines the theme of memory. And those are both at variance with the heavily literary nature of the form in this particular book. The reader is constantly reminded of, at first, Sir Thomas More's Utopia, and later on, other travelers' tales like Swift's Gulliver's Travels or Edgar Allan Poe's Narrative of A. Gordon Pym.

Lessing, not entirely sure that readers can comprehend her novel, appends a 20-page epilogue, explaining how she came to write this particular book. But such comments are better left to interviews with authors or to articles in scholarly journals. If the reader can trust the teller or the tale, then the author doesn't have to leap in to explain, point us in the right direction.

This novel, as part of the series, will appeal to certain groups of readers. Those who are Sufists will gobble it up. Adolescent males eager to read science fiction will surely be fascinated. Lessing fans, like myself, will read anything she writes. Devotees of Utopian literature will enjoy the changes Lessing rings on the form and focal points of that genre. Other readers, though, are quite likely to be disappointed in Planet 8.