Imagine the impossible: that the publishing industry hasn't changed since the 1980s, when Horror was the red hot thing and anything could sell. Allow for that, then take my word: a well-connected agent could sell a book today about Fat Elvis killing Diana. And he could sell it on spec.
When High Concept is king, the books half-write themselves. You begin with a premise, life-like or absurd, then continue asking questions until you have your story:
1) How could Fat Elvis have murdered the princess when he died almost exactly twenty years before her?
2) Why Fat Elvis instead of Thin Elvis?
3) Should the villain be an Elvis impersonator or the vengeful ghost of Elvis?
4) What possible connection could there have been between Fat Elvis and the princess, who was sixteen years old when he died?
5) How can I handle the whole thing without enraging fans of Diana or the King?
6) What if Fat Elvis didn't really kill her--not the real Diana? What if a, well, manitou* or djinn* had taken on Diana's form and Fat Elvis killed it to save her?
Not a thought of character, setting or theme have entered into the process so far. Everything is geared toward pulling off the Concept: convincingly and profitably.
Some fun books and films can result from this tack: Time After Time, with Jack the Ripper in the present, pursued by H. G. Wells...Snakes on a Plane...Cowboys and Aliens...But none of them nourish or fill us for long. The books and the films that stay with us tend to be far more organic: character, setting, theme and plot meticulously blended into one rich tapestry.
But great books are the bane of the Hollywood scouts because they don't make for quick pitches. No A or B Meets C or D applies to superior work; we can't fit the precis on the back of a stamp. Want a world-class headache? Imagine yourself as unpublished Stieg Larsson attempting to market his work in New York.
That said, now and then I wonder if Fat Elvis did kill Diana. And I know I could have sold a book called Goolie Gobblers: about toilet demons who snap off the goolies of Scotsmen who visit to do business. After all, I'd have had a long list of questions. Why do they only feed on Scotsmen? Are Scottish goolies packed with special vitamins? What do the demons do after goolie gnoshing? You know, we could have a winner here--with a small part for Fat Elvis.
*Two affectionate nods to British horror writer Graham Masterton--who could pull off a high concept novel bordering on the absurd because of his elegant style and wit. You can almost imagine him asking 'How the hell can I pull off a book about that?'...then laughing delightedly as he began. He's a wonderful writer, and well worth a look, if you haven't discovered him yet.