Some of my stories are inspired by just a love of a particular type of book, a particular interest, an interesting concept. Whether or not these things can push forward to an interesting manuscript varies on a number of factors, but they are a good, solid framework to begin writing a story on.
One of my current WIPs, Osland, a YA modern urban fantasy re-telling of the Wonderful Wizard of Oz, came from a much different place. A Broadway touring production of Wicked (great show, by the way) rolled into town earlier this year. I'd been waiting for a couple of years to see Wicked, so I snatched up a ticket and went to see the show.
Wicked the musical, of course, is an interesting case of setting and character reinterpretation. The musical is different in several key ways from Gregory Maguire's book but still obviously based on it. Mr. Maguire's book, in turn, is an even more extreme reinterpretation of Mr. Baum's original work.
What I find most fascinating is that the three different stories are so closely related to each other, yet different enough that consumption of any of the individual stories (even absent the medium differences) gives a totally different experience. Now, some people may enjoy one of those individual experiences better than the others. There were more than a few conversations in the audience about the relative merits of the plot differences between the book and the musical.
After I left that theater, Oz haunted my brain for days. For the first time since I had started writing, I felt like a story was "calling to me" rather than waiting for me to carefully consider and construct it. Whether or not my reinterpretation offers anything entertaining to readers remains to be seen, but I've really enjoyed writing the story nonetheless.
Obviously, I should go to the theater more often.