Eliezer wrote "the creative surprise is the idea that ranks high in your preference ordering but low in your search ordering." Colloquially, "that's great; I wouldn't have thought of that."
My intuition told me that Jürgen Schmidhuber likely did, and Google led me to his Formal Theory of Creativity and Fun and Intrinsic Motivation. I have not read it.
To me it seems that most creativity can be explained as either combining a few existing concepts, or introducing a small random change into something existing.
But then, how can something creative be great, considering that combining existing concepts should result in approximately average quality, and a random change is more likely to be bad than good? This is because people have a few creative ideas, and then select the best one. Or someone else selects the best idea, maybe from multiple people. Like, most books suck, but the few good ones become famous.
That is, explain creativity from more fundamental building blocks