It certainly is interesting how Lucas' ideas about Darth and Luke's father evolved. I have only read about a tenth so far and am finding out new things all the time. I did notice a quote that was a complete lift form 'Star Wars to Jedi: The Making of a Saga". Lucas does have a tendency to repeat himself though.

Also it never ceases to amaze me that the majority of the ideas that were thrown out or not achievable at the time were used in the prequels. It just goes to show that discerning individuals and restrictions are required when making a film. Don't read this as Lucas bashing. More that Lucas had a much better team around him at the time of Star Wars and Empire.