PD James is not just the author of a slew of detective novels. She has also slipped with ease into other genres (SF classic Children of Men comes to mind) and she's a baroness who sits in the House of Lords. She is also an author of fanfiction. Because how could her latest offering, Death Comes to Pemberley, about a bad murder that disturbs the peaceful happy ever after of Darcy and Elizabeth, be described as anything else?

This high-profile outing for one of literature's most maligned genres finally shows that fanfiction is a worthwhile literary pursuit. Though this respectable end of fanfiction has always been around in books like the brilliant Wide Sargasso Sea by Jean Rhys, or Susan Hill's Rebecca prequel Mrs de Winter, the current literary trend seems to explore retreads of another author's story. Along with PD, Anthony Horowitz is re-imagining Sherlock Homes (Stephen Moffat and Guy Ritchie are weighing in with their takes too) and Jeffery Deaver has recently given us his spin on James Bond.

Are these books so different from what you might find trawling the annals of fanfiction.net – an archive so extensive it features over 70 stories reworking the characters and situations of, um, Tetris? Well, they're certainly viewed very differently. While respected authors publish real, paper books riffing on characters created by authors long dead (and therefore, crucially, out of copyright), fanfiction is still seen as geekier than geeky, the pursuit only of the friendless, usually female internet nerd, creating panting fantasies, riven with author insertions.

And unlike those big glossy-covered hardbacks, fanfiction is never going to make its authors any money. There has never been a test case, and while some claim it counts as "fair use", the legality of fanfiction is pretty much a grey area. Wikipedia, unsurprisingly, covers this in mindbending detail. While those legal issues come into play if the work is still in copyright, if the author is still alive things can get even more morally complex. Some authors, such as Anne Rice and George RR Martin have specifically condemned fanfiction, asking their fans not to play in their personal sandboxes. Martin even went so far as to dismiss the process as "bad training for any aspiring writer".

Fanfiction, playing with characters and worlds already created elsewhere, can be a thrilling creative outlet for all kinds of people. The most enjoyable works of fiction present us with convincing worlds; we believe our favourite characters existed before "once upon a time" and go on existing after the final full stop. It's not surprising then, that the best stories can be irresistible playground to some writers. Yes, quality varies. A lot of fanfiction is, indeed, terrible: it's amateur fiction published, unedited online. What were you expecting? But, like any kind of literature, fanfiction can be sublime or ridiculous. There are some real gems out there, that are every bit as original as works with no previous owners.

Isn't it time we gave the art of remixing stories it a little more respect? After all, it was good enough for Shakespeare.