It's a little difficult to describe the Thursday Next novels without making them sound precious and twee. In fact, they are somewhat precious and twee, but also great fun -- especially for those with a literary turn of mind and a taste for offbeat comedy in the tradition of Terry Pratchett and Douglas Adams, Norton Juster and Lewis Carroll. Indeed, one of the pleasures in reading the three installments of the adventures of Thursday Next lies in recognizing the myriad bookish allusions, some obvious, some very sly indeed. For instance, in The Well of Lost Plots a character is about to be auctioned off as "Lot 97." Fans of Robert Heinlein's juveniles will remember that Citizen of the Galaxy opens with the words: " 'Lot 97,' the auctioneer announced. 'Boy.' " Even more obviously, this new book -- my favorite in the series so far -- also includes a brief appearance by Gully Foyle (the hero of Alfred Bester's science fiction classic The Stars My Destination, the likely inspiration for the "book-jumping" in which Fforde's characters engage), an army made up of thousands of Mrs. Danvers clones (Mrs. Danvers being the evil housekeeper of Rebecca), the upcoming nuptials of Professor Plum and Miss Scarlet (from the game Clue) and the hitherto untold story behind why Molly Bloom's soliloquy at the end of Ulysses doesn't contain any punctuation (in a word, grammasites -- a kind of textual parasite).

Already confused? Let's look at the backstory. In his first novel, The Eyre Affair, Jasper Fforde imagined an alternate England, in which the Crimean War has gone on for more than 100 years and all culture revolves around books. Poems, plays and novels determine politics, fashion, leisure-time activities, almost everything. Shakespeare worship is a cult, young men dress like Byron, there's even a brisk trade in fake manuscripts and lost masterpieces. At the climax of that thriller -- largely a pastiche of a police procedural, enhanced by fantasy elements (time travel, in particular) -- special operative Thursday Next actually uses an experimental Prose Portal to enter the text of Jane Eyre. Carefully keeping out of the way of the main action, she there defeats her evil nemesis, Acheron Hades, but in so doing also changes Charlotte Brontë's "original" downbeat ending, one in which Jane weds the wrong man and emigrates to India. Happily, polls have demonstrated that, with the exception of a few diehard conservatives, most readers prefer Thursday's new conclusion, with the longsuffering Jane happily marrying the maimed Rochester.

Lost in a Good Book picks up right after The Eyre Affair. Thursday has become a minor celebrity (talk shows, news programs) and has finally married her own beloved Landen. Before long she's even expecting a baby. But then a lost Shakespeare play, "Cardenio," shows up; the evil Goliath Corporation starts pressuring her to release their agent Jack Schitt from imprisonment inside Poe's maddening sing-song classic "The Raven"; and Landen disappears so entirely that almost nobody realizes that he ever existed. At the same time, someone keeps trying to kill Thursday, someone who can control coincidences and meddle with memories. As if that weren't enough, our tough-gal heroine learns from her time-hopping father that all organic life on Earth is about to be transformed into a disgusting pink sludge. What's a girl to do? To help resolve all these disparate plot lines, Jasper Fforde introduces a wholly new element to an already idea-rich series: The BookWorld. The gradual delineation of this strange literary realm provides a secondary narrative line for Lost in a Good Book and the scene for all the action in The Well of Lost Plots.

If matters already seem a mite disorienting, just take a breath. You ain't heard nothing yet.

Borges once imagined the universe as a library. Fforde adapts this idea but brings to it his own grace and antic disposition. All books, it turns out, are essentially copies of living Platonic originals that are kept in the Library, an otherworldly building consisting of 26 floors, one for each letter of the alphabet. In the basement of this vast but orderly structure lies the Well of Lost Plots, the realm where unpublished manuscripts are polished and readied for publication. Nearby looms a vast word sea, the final resting place for discarded books once they are broken down into their component elements. Novels are inhabited by characters who, like those in Flann O'Brien's At Swim-Two-Birds, are able to carry on their own private lives when not on story duty. But this isn't a peaceable kingdom, by any means. Literary texts are subject to depredation by various parasites, some of them quite deadly, like the "mispeling vyrus," which can almost instantly turn a house into a horse, a nose into a rose. (In the vicinity of such dangers, workers attach a carrot to their uniforms: When the vegetable starts to sprout feathers, it's time to get out. By the time it's actually a parrot, it's usually too late.) There are other dangers in the Library, including The Questing Beast, Big Martin, uppity characters like Heathcliff, unhappy Generics waiting for their big break, and various renegade Page Runners and Bowdlerizers who jump into books where they don't belong.

The BookWorld is overseen by Text Grand Central with the help of a special intra-literary police force. Jurisfiction operatives include characters from Dickens, Swift and Shakespeare but also a few Outlanders (i.e., living people); its headquarters lies at Norland Park, the Dashwood home in Sense and Sensibility. This elite team's mission is to preserve the integrity of the Library's books from attack by parasites, renegades and other enemies of textual stability. In Lost in a Good Book Thursday needs to make her way into this world to save Landen and to testify in her own defense over a serious infraction -- her high-handed change to the ending of Jane Eyre. Before long, though, she is enlisted into Jurisfiction as an apprentice to Miss Havisham, a gun-toting, race car-obsessed Prose Operative of the highest distinction.

At the opening of The Well of Lost Plots, Thursday has gone into temporary hiding from her Outlander enemies deep inside a trashy police novel called "Caversham Heights." Through a Character Exchange Program she's pretending to be Mary Jones, a subordinate to detective Jack Spratt. But most of the time she's actually out on Jurisfictional exploits -- this is a very touristy novel, as Thursday visits various book realms inside The Well. Readers will recognize scenes adapted from "Star Wars," "Hill Street Blues" and a celebrated John Collier fantasy classic. Eventually one doesn't even pause over the oddity of a sentence like the following: "The minotaur had given Havisham the slip and was last seen heading towards the works of Zane Grey, the semi-bovine wasn't stupid -- he knew we'd have trouble finding him amongst a cattle drive." There's a particularly hilarious chapter in which Thursday is sent in to alter slightly Enid Blyton's Shadow the Sheepdog and finds herself in a terrifying town right out of Shirley Jackson, Jonathan Carroll or Richard Matheson. Throughout, Fforde neatly cross-references the real world for humorous effect; for instance, a computer network connects people in Jurisfiction, and its messages are represented by footnotes. Of course, all such networks are eventually prey to spam:

"Dear Friend, I am a fifty-year-old lady from the Republic of Gondal. I got your details from the Council of Genres and decided to contact you to see if you could help. My husband Reginald Jackson was the rebel leader in Gondal in Turmoil (R.R.P. 4.99 pounds) and just before he was assassinated he gave me 12 million dollars."

It's even funnier when you recall that Gondal was the imaginary realm created by the Brontë children.

Perhaps the book's greatest tour de force occurs when Miss Havisham and Thursday are sent to conduct a rage-counseling session with characters from Wuthering Heights. Everyone naturally loathes Heathcliff, except Catherine: "I love Heathcliff more than life itself," she exclaims. At which point, "the group groaned audibly, several members shook their heads sadly, and the younger Catherine did the 'fingers down throat' gesture." Only then does the sullen Heathcliff arrive late for the meeting:

" 'The devil take your sessions, Miss Havisham,' he said angrily. "Who is the star of this novel? Who do the readers expect to see when they pick up this book? Me. Who has won the 'Most Troubled Romantic Lead' at the BookWorld Awards seventy-seven times in a row? Me. All me. Without me, Heights is a tediously overlong provincial potboiler of insignificant interest. I am the star of this book and I'll do as I please, my lady."

After this speech, "he pulled a signed glossy photo of himself from his breast pocket and passed it to me with a wink. The odd thing was, I actually recognized him. He had been acting with great success in Hollywood under the name of Buck Stallion, which probably explained where he got his money from; he could have bought Thrushcross Grange and Wuthering Heights three times over on his salary."

And then, just at this point, a shot suddenly rings out (a standard Narrative Turning Device), followed by submachine gun fire -- a ProCath terrorist attack. After all, "support of the young Catherine and hatred of Heathcliff run deep in the BookWorld." With this irruption of violence, The Well of Lost Plots starts to accelerate. Soon a Jurisfiction agent is murdered, and only another agent could have committed the crime. Which one? And why? More characters die or disappear. Are the crimes somehow linked to Thursday's Outlander enemies or to the advent of the new UltraWord operating system, "the ultimate reading experience"? Or to something else entirely? And finally was Flatland truly the last original plot?

Enough. The BookWorld seems to have encouraged Fforde's rogue imagination to escape all fetters and go really wild. According to a prefatory note, there are even special features available on a Jasper Fforde Web site. I haven't gone there, so I expect that others may have already pointed out some small literary errors: Captain Nemo does appear in a sequel to Twenty Thousand Leagues Under the Sea; it's called The Mysterious Island. The apocryphal Sherlock Holmes story is properly titled not "The Curious Experience of the Patterson Family on the Island of Uffa" but "The singular adventures of Grice Patersons in the Island of Uffa." Shakespeare's hero is Benedick, not Benedict. Still, none of this matters. As one of Fforde's characters observes, "If you don't make mistakes, you're not trying hard enough." Fforde may be straining just a bit in The Well of Lost Plots -- I haven't even mentioned Acheron Hades's vengeful sister, the revolt of the nursery-rhyme characters and other so-called Orals, Thursday's amnesia, the sudden appearance of Edward Rochester during a trial before the King and Queen of Hearts, Mrs. Tiggy-Winkle and Mr. Toad, and the pictorial advertising at the back of the book.

In many ways, The Well of Lost Plots is a far more ramshackle novel than its predecessors, with a hasty finale and the convenient introduction of a deus ex machina. Not that it matters much: A book is, after all, "one of the most stable and complex Imagino-Transference technologies ever devised." Certainly no one at this Book World would disagree with that.

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