Yes. I recommend _The Secret History of Star Wars_ - as a longtime EU fanatic, I was shocked how many pieces fell into place reading it.

(Incidentally, the narrative of _The Secret History_ means that this sale is particularly interesting; we can see the sale as the definitive death of Lucas's youthful dream of a paradise for indie filmmakers like he was, who were going to revolutionize the staid Hollywood establishment of bloated corporate giants like Disney, the dream which motivated him to produce sequels to the standalone movie _Star Wars_ as cash cows.)

I was a child when the original Star Wars came out, and I was never under the impression that the entire triple trilogy had already been written, though it was always supposed to be nine movies. If anything, he had an idea for its direction, but in hindsight I think that was more salesmanship on his part.