THE HISTORY OF THE SIEGE OF LISBON. By Jose Saramago. Translated from the Portuguese. By Giovanni Pontiero. Harcourt Brace: 320 pp., $24

It begins with an explosion of words, as if they were stored in a silo and had spontaneously combusted. For a while the air is choked with clouds of chaff: paragraphs that run for pages and looping dialogue whose tenses and speakers change repeatedly in the same sentence.

The dust settles. We perceive a middle-aged Lisbon proofreader in a foggy philosophical disputation with the author of the book he is correcting. It is an account of Alfonso Henriques, Portugal’s first king, capturing Lisbon from the Moors 850 years ago.

Without transition, we go from present-day Lisbon back to 1147. A muezzin is about to call out the noon summons to prayer. He could be a condemned man springing the trap on his own gallows: The Christians will use the call as a signal for their attack.

Despite its title, Jose Saramago’s “The History of the Siege of Lisbon”--also the name of the book his proofreader is working on--is essentially rooted in the present. The present is permeable, though; the past leaks in.

Saramago’s hero is Raimundo Silva, a bachelor who has chosen his tidily definite occupation to prudently confine a soul as boundless as the paradoxes of history, language and erotic passion. Silva’s comically suggestive adventure begins with an act of revolutionary imprudence that upsets the laws of literature and time. Such a thing must have consequences; soon the laws of bachelorhood are upset as well and Silva finds himself inextricably and entrancingly in love.

Saramago is one of Europe’s most original and remarkable writers; among other reasons, he is remarkable for being utterly and indelibly Portuguese, a quality that Europe--not to mention the United States--has little acquaintance with. Like the works of Eca de Queiroz and Machado de Assis--a Brazilian but Portuguese in spirit--his writing is imbued with a spirit of comic inquiry, meditative pessimism and a quietly transforming energy that turns the indefinite into the unforgettable.

Portugal, at least in the north, is a foggy country. Its history of decline--imperial at first, later national--is longer than that of any other European nation. Its reigning spirit is saudade, or a kind of pleasurable melancholy. That is a stereotype, of course; like most stereotypes, whatever truth it doesn’t render, it tends to generate. As Silva, already love-stricken and gazing out of his window at night, reflects: “Dear God, what sweet and gentle sorrow. May we never be without it.”

Centuries of fog, decline and melancholy. If Elizabethan national resurgence had something to do with Shakespeare’s unbounded universality, how could a great Portuguese writer, in this doleful trio of national conditions, do anything but flower into skepticism about history and reality? The flowering in this desert--or marsh--is brilliant: fantasy, humor and a need to read the world’s messages backward for what they conceal.

Working on still another history of one of Portugal’s signal happenings, Silva is, accordingly, in a state of depressive skepticism. Its glib conventional version, based on the thinnest of sources, offends him. A sentence stands out--arrogantly, it seems to him. It states the conventional wisdom: that Alfonso was helped in the siege of Lisbon by battalions of crusaders on their way to the Holy Land.

A scandalous impulse takes hold, sheer blasphemy in the proofreaders’ credo. Silva inserts a “not” in the sentence--the crusaders now refuse to help--and sends the proof off. Terror and exaltation follow.

As he awaits his nemesis in the form of a call from the publishers, he goes to a cafe. It is full of Moors, it seems to him; they are sipping coffee, reading the papers and chuckling over the Portuguese defeat. When Saramago offers a hallucination, it is an ironic commentary on reality--in this case, on the reality of written history. If historians can establish the past with their monographs, why can’t Silva establish it otherwise with his “not”?

The conceit is not pursued. Yet as it turns out, Silva’s act has indeed changed history, only it is history of a different kind. After 13 days, his bosses send for him, but they are too shocked, frightened even, to quite be angry. A world in which writers write, editors edit, publishers get rich and proofreaders correct spellings is threatened. An erratum notice is inserted in the finished book, and Silva is let off in exchange for an apology.

The scene’s silences and indirections are rich in comic implication. After his boss says he is certain that this will never happen again, Silva maintains a moment or two of obdurate silence. Characteristically, Saramago uses an image that lets in a wider, disconcerting light: “Let us suppose that a man has asked a woman, ‘Do you love me,’ and she remains silent, simply looking at him, sphinx-like and distant, refusing to utter that ‘No’ that will destroy him, or that ‘Yes’ that will destroy both of them.”

A new editor, Dr. Maria-Sara the “Dr.,” used with just a first name, is a wry play on residual Portuguese resistance to professional women--is assigned to check Silva’s work. Their first meetings are tense; he finds her intimidating. At the same time, he is attracted and, inexperienced in love, he does not quite realize that she is too. Her initial severity, in fact, conceals an awed admiration for his rebellion and what she calls, after the initial tension is dispelled, his “lateral thinking.” She insists, in fact, that he write his alternative history, stemming from that “not.”

From here on, the “Siege of Lisbon” alternates between Silva’s new version of history and the steadily warming relationship between Silva and Dr. Maria-Sara, ending in a full-blown affair.

The revised version of how Lisbon was taken, without the crusaders’ help, is an awkward and sometimes very funny effort to improvise historical alternatives so that they fit in with the undoubted fact that the Moors were defeated. Silva devises some elaborate technology and a German knight-inventor who puts it together and then, after being killed, becomes the source of miracles and pilgrimages. A Portuguese history requires its miraculous side; on the other hand, to fit modern ideas, it also needs its social conflict.

Silva has the Portuguese troops go on strike for a fair share of profits. “You’re just getting Portuguese history started,” a strike leader tactfully tells the king, “and you want to do it justly. Do not let Portugal become crooked, I implore you.” The irony is wonderfully deadpan: Justice has the Moors, who had been there for centuries, despoiled, massacred or driven out.

The siege sections are deliberately ramshackle, and here Saramago’s elaborately interlocking sentences and incessant asides can become tedious. His point, of course, is that Silva’s history has the same superficiality and arbitrariness as any other history. The “not” was his only real feat. Not because, after demolishing history, it put anything in its place, but because it ignited Dr. Maria-Sara.

The brilliantly original achievement of “Siege” is the comical, hesitant and powerfully erotic progress of their mutual courtship. Here the looping sentences, the excursions, the indirections and the very wordiness make splendid play. They give the pulse of the thousand hesitations, terrors and hopes of such an affair. Through pricklinesses, veils of timidity, crossed messages, retreats and valiant and terrified advances, these two splendidly human figures conduct the only lasting and authentic siege of Lisbon.