Doing some further reading in the book: it appears that not all the actors got on well with Marquand. Carrie Fisher (who seems to have particularly disliked him) describes Marquand's behavior on set as "kowtowing" to Famous Actor Harrison Ford, but treating her and Mark Hamill "badly" because they were less famous. She wasn't impressed, and neither apparently was Ford.
Another thing that is very obviously evident is George's overriding concern with the budget, above just about all other aspects of the picture. At times it interfered with the shooting of the film. Marquand had to beg, for instance, for permission to have a giant Rancor hand made to shoot closeups of Mark Hamill in; Lucas had initially refused because of the expense.
The story about GL nixing a costly animatronic Sarlacc tentacle (only to later renege on this decision when he decided the monster had to actually be seen) is also mentioned.
Producer Howard Kazanjian reveals that (as with Ghost Anakin) seeing Vader make the decision on camera to kill the Emperor was his idea:
"Darth Vader is standing there as the Emperor is zapping his son," Kazanjian would say. "Then in dailies, we're watching and talking, and I turned to George and said, 'George, we don't see Darth Vader making the decision. There are no close-ups of him.' So we went back and George shot Darth Vader standing there kind of turning his head left and right, and making the decision to throw the Emperor into the pit."
The screening of Marquand's first cut of the film was apparently a disaster; Lucas was not happy with it at all. (Its style apparently felt "not like Star Wars," and in some places the editing was just plain bad. For instance, in the scene where Vader talks to Jerjerrod as they walk down the Death Star hangar bay, "the screen direction was wrong, backward," as Kazanjian pointed out.) However, Sean Barton, Marquand's film editor, had produced a different cut that Lucas liked a lot more.
Oh, and the book also explains some of the weirdness of that leaked clip of the early Rancor scene: the original attempt at the scene used a large Rancor suit, Godzilla-style, but the results were so ugly that they had to be essentially excised from the final film and replaced with a puppet matted into Hamill's scenes.