Between all the undead in Austen, and the walking dead guy around Salinger, people are starting to wonder what the effects of all these prequels, sequels, and parodies might be. I’ve got an answer you might not like: hilarity!

Books that are still in copyright are a more complicated challenge for the would-be writer of prequels and sequels. This is partly because a lot of money is sometimes at stake. The Mitchell estate was so fussy about protecting “Gone With the Wind” because the franchise is a gold mine. Alexandra Ripley’s “Scarlett,” an authorized sequel, was a huge best seller in 1991, even though the critics sniffed at it. Living authors, moreover, are understandably attached to their characters and creations and may not want to think of them as demented, say, or having problems with bladder control. Where do you draw the line between critique or parody and outright exploitation?

Yet the urge to write sequels and prequels is almost always an homage of sorts. We don’t want more of books we hate. The books that get re-written and re-imagined are beloved. We don’t want them ever to be over. We pay them the great compliment of imagining that they’re almost real: that there must be more to the story, and that characters we know so well — Elizabeth Bennet, for one, or Sherlock Holmes, who has probably inspired more sequels than any other fictional being — must have more to their lives. In a couple of quite good sequels recently — “A Slight Trick of the Mind,” by Mitch Cullin, and “Final Solution: A Story of Detection,” by Michael Chabon — we even get to watch Holmes grow old and discover love of a sort.

Certain books are more than mere texts — words on a page or, these days, an electronic reading device. They’re part of our mental furniture.