Want to know what high concept is? Then read this post by agent Holly Root at Waxman Literary. I rather liked it. Now if only I could think of one.
I still haven't read Twilight (will eventually) but I started Charlaine Harris's Dead Until Dark (pub 2001) and there it was — a glowing vampire. Apparently, glowing vampires didn't start with Meyers. It takes more than a glowing vampire to make a high concept, of course, and Meyers managed it. I think, from the periphery, that Twilight is Wuthering Heights with vampires directed at teens. Will have to read to know for sure, of course.
What do you think about high concept? Does it come easy to you? Make sense? I'm still mulling it.