IN A WORLD where a madman can take a hammer to Michelangelo's "Pieta" and Taliban zealots can blow up 1,800-year-old statues of the Buddha, even deathless art has a significant mortality rate. But great books really are immortal. Destroy the manuscript of "A Tale of Two Cities" and the scholars will weep, but Sydney Carton will go on doing a far, far better thing than he has ever done, in cheap paperbacks and the finest calf bindings, wherever people read.

For the unfortunate people in "The Eyre Affair," though, not even fictional characters are safe from the machinations of archvillain Acheron Hades. The fiend has hijacked a device that can send ordinary humans into the pages of a book - or pull fictional characters out. Removing a character from a late edition changes only that copy of the book (and other copies based on it), but once Hades gets his hands on an original manuscript, he can alter the work for all time. He starts small, by murdering a minor character from "Martin Chuzzlewit," just to show he can do it: "On the bottom of page 187 there was a short paragraph outlining one of the curious characters who frequent Todger's, the boarding house. A certain Mr. Quaverley by name. He is an amusing character who only converses on subjects he knows nothing about," a professor of English literature, Dr. Runcible Spoon, tells Special Operative Thursday Next of the Literary Police. "If you scan the lines I think you will agree with me that he has vanished."

Although losing Mr. Quaverley looks bad, the book can survive without him. (In fact, he doesn't exist at all in our world's version of the Dickens novel - I checked.) But when Hades lifts the original manuscript of "Jane Eyre" from the Brontee museum and carries it off to the People's Republic of Wales, the British authorities take the threat seriously indeed. Without Jane Eyre narrating, there could be no "Jane Eyre."

While the Hades caper raises questions that have engrossed thinkers from Walter Benjamin to Jacques Derrida, Fforde has more in common with Douglas Adams or Lewis Carroll. After all, mathematicians love to quote "Alice in Wonderland," but you don't need to share Carroll's degree in symbolic logic to enjoy his books.

In most books, when the hero revisits his past he does it metaphorically. But Fforde's open-armed satire includes science fiction in its embrace. Thursday is a second-generation special operations officer. She belongs to SO-27, the Literary Detective Division, but her father was a ChronoGuard, a member of SO-12, until he went rogue. "My father had a face that could stop a clock. I don't mean that he was ugly or anything; it was a phrase the ChronoGuard used to describe someone who had the power to reduce time to an ultraslow trickle."

Fforde's love of absurd, intricate devices reaches a high point in the character of Mycroft, Thursday's mad-inventor uncle. Among his contrivances are a method for sending pizzas by fax and a 2B pencil with a built-in spell checker. ("Did the memory erasure device work, Uncle?" asks Thursday. "The what?" "The memory erasure device. You were testing it when I last saw you." "Don't know what you're talking about, dear girl.")

As Thursday pursues Hades through this world and the next in an effort to rescue those dear to her - not only Jane Eyre, but Uncle Mycroft and Aunt Polly, whom Hades is holding hostage to make sure of the inventor's help - she changes literary history. In Thursday's world, "Jane Eyre" ends when Jane decides to marry her cousin St. John Rivers and go with him to India as a missionary. "It was generally agreed that if Jane had returned to Thornfield Hall and married Rochester, the book might have been a lot better than it was." When reading "Jane Eyre," did you ever wonder how Jane managed to hear Rochester calling to her from miles and miles away at the exact moment when she was about to agree to St. John's proposal? It takes a bold adventurer to play fast and loose with literature, and that's what we have in Thursday and Fforde.