I was curious about this so I borrowed Iger's book from my library. Here is a summary of what Iger actually says:
Iger respectfully approached George about the prospect of selling. They had some history, having collaborated on Young Indy. George came back about 7 months later wanting the same deal as Pixar. Disney calculated that Lucasfilm wasn't worth that due to the lack of upcoming movies or directing talent that Pixar came with.
George wanted to maintain creative control but Iger insisted that was not an option. They both walked away from negotiations on 2 separate occasions over this. But, an upcoming change to Tax laws meant that Lucas would lose $500 million on the sale, so there was an incentive for him to do the deal before that came into effect.
George reluctantly agreed to be a consultant but there was no contractual obligation for Disney to use his ideas, although Iger was happy to hear them.
The main disagreement arose because Disney purchased the rights to Lucas's story treatments. George took this to mean that they would be used, and when the producers of Episode 7 brought their story to him he was surprised and pissed.
George definitely wasn't a victim in all this and he even did a few questionable things himself. To exert a little bit of control, he put Kathleen Kennedy in charge of Lucasfilm before the sale was finalised, which came as a surprise to Iger. Clearly that backfired on George when Kathleen agreed to ignore his story treatments.
Then there was George's "white slavers" diatribe during his Charlie Rose interview. Iger states that one of the last things they negotiated during the sale was a "non-disparagement clause". It might be argued that George breached that clause, but Melody, George's wife, emailed an apology and George later called Iger to smooth things over.