How novels turn into TV and movies is pretty well understood, but just how do stories make that reverse leap from our screens to the page? And could your novel, that one you have patiently gathering digital dust on your hard drive, be next?

Well, probably not. io9-commenter, and author of the novelizations for Man of Steel, The Dark Knight, Underworld, Star Trek, and short stories for Buffy, and Farscape, Greg Cox explains:

Media Tie-In Writing 101: No, you cannot just write your novel and then somehow pay the licensor for the privilege—although this is a VERY common misconception. (Just a few months ago, a fan at a convention asked me how much I paid CBS to be able write Trek novels—and I've gotten this question a lot.)

Here's how it works: The Publisher does a deal with the Licensor to publish SPACE VIXENS novels, based on the popular movie/TV show/comic book/computer game. The Publisher then hires freelance authors to write the books on a work-for-hire basis. The Studio must approve all outlines in advance and has final approval over the ms. as well. In short, the writer is a hired contractor. The Publisher pays the Licensor for the rights to publish the book and pays the writer to the write it.

In other words, you cannot write a 400-page SPIDER-MAN novel on spec and then arrange to get it published somehow. That's not how it works.

I harp on this only because it breaks my heart when people keep asking me how to get their tie-in books published—after they've already written the darn thing!

Okay, noted. But, once the contract is in hand, just how much latitude on the plot does the author have? At lot of it depends on what is still going on with the original series:

Regarding the reset button, a lot does depend on whether the original series is still a going concern or not. You have a lot more latitude when it comes to writing for a cancelled series than when writing for one that is still on the air.