I finished the newest Thursday Next book, Thursday Next: First Among Sequels, a couple of days ago. Unlike Speed 2, Star Wars Episode 1, or Freddy vs. Jason, this was a sequel that could stand proudly among the original quartet of Thursday Next books.
For those of you who are woefully unacquainted, Thursday Next is a person who exists in a sort of parallel reality to our own, in which the Crimean War dragged on into the mid-1970s, croquet is a full-contact sport, and a special division of the police is devoted to literary detective work. This is what Thursday Next does. She becomes so noteworthy at it that the book world takes notice and she is invited to become a Jurisfiction agent and work within the books themselves. This series was what inspired me to read Great Expectations (Miss Havisham was Thursday's partner in Jurisfiction; she disliked men, raced cars, wore tennis sneakers with her wedding dress and socialized occasionally with the Red Queen from Alice in Wonderland).
It doesn't matter if you haven't read all of the books that the series references. I'm sure there are a number of hilarious Jane Austen jokes that have gone flying over my head. But there is enough of other types of humor in these books to make them worthwhile: the over-the-top name games are an obvious example ("Agents Hurdyew, Tolkien and Lissning heard you talking and listening..."). There are also hilarious concepts, like Hamlet hiring a conflict resolution coach, or the stupidity surplus I mentioned earlier that's featured in this book, or the Dirty Bomb that the Racy Novel is threatening to unleash on all of literature, that would sprinkle dirty words and sexual innuendo where they were never intended to be. I've read all of Jasper Fforde's work except for The Fourth Bear and I'd have difficulty outlining the plots of any of them, even the one I just read. But they're so good it doesn't matter. If you've never partaken, get lost in one today (if you have partaken, you're probably groaning at that!). First Among Sequels could stand alone, but I recommend starting at the beginning with The Eyre Affair.