THERE IS A LOT of writing (and filming) about the supernatural going on currently, nearly all of it cynical. It's cynical in the sense that the authors don't believe for a second that there really might be a vampire lurking in Rock Creek Park, or that some large dog is possessed by the powers of evil. All they believe in is the marketability of plots like that. Such cynicism has a price. Almost inevitably their books and movies come out shallow.

Serious writing about the supernatural is quite another matter. That can wind up deeper and more powerful than almost anything else in our literature: The Divine Comedy, for example, or Beowulf. The reason is obvious. A universe in which the supernatural operates is a universe charged with meaning. And to invest action with meaning is maybe the most important thing literature does.

Charles Williams' novel All Hallows Eve is one of the most powerful works of supernaturalism to appear in our century. It comes, appropriately enough, out of the same nexus as many other such works: The Lord of the Rings, Perelandra, the Narnian chronicles. Williams was a friend and contemporary of J.R.R. Tolkien and C.S. Lewis--and when his work took him to Oxford during the Second World War, he promptly became the third great central figure in the informal literary group known as the Inklings.

Williams is not nearly so well known as Lewis and Tolkien, and there are several reasons. One is that most of the time he is not nearly so good a writer. Another is that he's a much better mystic than either of them--and mystics make harder and higher demands on their readers than storytellers (Tolkien) and allegorists (Lewis). A third is that unlike them he does not write the kind of fiction available to both children and adults, but a kind available to adults only. All Hallows Eve will never be a TV special--or if it is, it will be so debased and vulgarized as to make most TV specials of great books seem works of astonishing fidelity.

The book opens in London in 1945. The war has just ended. A loving young wife named Lester Furnival is waiting on Westminster Bridge to meet Richard, her husband of six months. There is a strange lull over the city as she waits: not a sound to be heard, not another person in sight. Finally, just as she is impatiently leaving the bridge to search for him, Richard comes walking into sight. His face goes white when he sees her, and then he springs toward her.

But she is angry at having had to wait so long; she throws up a hand to repel him. The gesture has extraordinary force. Richard is driven backward by it as if by a wind. As he vanishes, Lester realizes that for the moment they were together, the sounds of the city had returned. Now they fade again. It is then that she realizes she is dead. It takes her somewhat longer to realize that she is in what Williams always calls The City, one of many mystical cities that coexist with the actual living London of 1945 (and of 1982). Most of the newly dead are in that city, though rarely present to each other, since for each of them it is a slightly different place, depending on what they valued in life.

But people who die together are likely to enter The City together, and Lester had been with her friend Evelyn when the crash took them. The two young women soon encounter. It is not an easy or a happy meeting. The disguises that masked their friendship when they were alive are gone. It is clear to both of them that Lester, who was a much more vivid and interesting person, had been a kind of fire at which Evelyn warmed herself. And clear that for Lester Evelyn had been a convenience, someone to call if she happened to want company when she went shopping. Clear, in short, that each had used the other. One main theme in the book is the progressive salvation of Lester and the progressive damnation of Evelyn as they face what they were, and do or don't decide to change.

But it is by no means the only theme. All Hallows Eve has a complex and even thrilling plot. The action swirls around a great religious leader named Simon Leclerc: a prophet, a worker of miracles, the head of a world cult. He is something like the Rev. Mr. Moon raised to the fourth power--or he seems that way to outsiders, at least. He is actually the most powerful magician who has lived in several hundred years, and he is a tall, godlike, ascetic, and wholly evil person, a negative of Jesus Christ, whose very distant cousin he in fact is. What he promises human beings is peace; what he actually seeks is to rule them, not only in life but even after their deaths.

All the other characters meet Simon, and all in the end must choose between serving him and resisting him. Richard, Lester's husband, meets him because Richard is a British diplomat; and Simon has become so great a force that the government must deal with him almost as if he were another country. Lester and Evelyn meet him through his daughter, who spends many of her nights in the mystical city.

This tormented girl of 21 needs some explaining. She has no idea that she is Simon's daughter. Her name is Betty Wallingford, and she supposes her father to be Air Marshal Sir Bartholomew Wallingford, a man who has exercised his fatherhood chiefly in being away on duty with the RAF. Her mother, Lady Wallingford, is the prophet's chief disciple, and a formidable woman.

Betty is not the result of clandestine passion. Simon and Lady Wallingford slept together once only, and that for the specific purpose of producing a child of his flesh, over whose spirit he will have a special control.

With the willing consent of Lady Wallingford, Simon has for some years been putting Betty into night trances, forcing her soul out of her body, and sending it into The City, where past, present and future are, if not one, at least intermixed. Through her eyes he can see several months ahead. This increases the accuracy of his prophecies greatly . . . and the only cost is the steady deterioration of his daughter's health. No problem there; he intends to kill her soon, anyway-- just as soon as his control is complete. Then her soul is to be stationed permanently in The City, to serve as his agent.

A sheer accident frustrates this plan. Years ago, Betty happened to attend the same girls' boarding school as Lester and Evelyn--and in fact to have been Evelyn's chosen victim among the younger girls. That fact, too, has force in The City, and the two dead women perceive the living visitor, and follow her home. One of them soon joins Simon; the other sets herself to save Betty. Few supernatural struggles, I think, have been more splendidly portrayed. The climax comes in a great ritual, half magic and half Christian, on All Hallows Eve, more commonly known in this country as Halloween.

Baldly summarized this way, the book sounds downright lurid. It isn't. It is solemn and august and even a little bit holy. Best of all, it succeeds in making The City a place more real than the earth we live on. Words spoken there are almost palpable. When Evelyn, soon after the crash, is protesting the unfairness of everything, she whines to Lester, "Why are we here like this? I haven't done anything. I haven't; I tell you, I haven't. I haven't done anything." And Charles Williams adds, "The last word rose like a wail in the night, almost (as in the old tales) as if a protesting ghost was loosed and fled, in a cry as thin as its own tenuous wisp of existence, through the irresponsive air of a dark world, where its own justification was its only, and worst, accusation." That is, Evelyn in protesting that she hadn't done anything was using the phrase in its conventional sense, to mean that she had done nothing wrong. But in The City the literal meaning inheres in the words (and is true)-- that in her 25 years of e salife she had been almost entirely passive and inert, that she had wasted the gift of being.

Or again, Lester, trying to rouse her friend into doing something now, exclaims at one point, "Oh, my God!"

"It was," Williams says, "the kind of exclamation she and Richard had been in the habit of throwing about all over the place. It meant nothing; when they were seriously aggressive or aggrieved, they used language borrowed from bestiality or hell. She had never thought it meant anything. But in this air every word meant something, meant itself; and this curious new exactitude of speech hung there like a strange language, as if she had sworn in Spanish or Pushtu, and the oath had echoed into an invocation." Everything in The City is like that, and it makes The City an exciting if scary place to visit.

Philip Larkin speaks in his greatest poem of people in the 20th century surprising in themselves "a hunger" to be more serious than they are. For anyone with that hunger, All Hallows Eve is a magical book indeed.