I can relate! I'm working on a long-gestating book project myself (about the DC Animated Universe), and although people are telling me they can't wait to read it, I have to keep telling them it's a looooong way off from completion, as I'm still in midst of conducting interviews for it (Although I did get to talk to two new people this week, so that's good.)
OK, let me first qualify this by saying that I'm going from memory here, as I no longer recall exactly where I first read this stuff. (Perhaps while flipping through Nichols' own bio? I honestly forget.)
Nichols objected to a passage where Shatner talked about the fact that she and GR had had a romantic relationship sometime before TOS (I forget if it was an extramarital affair or not). I think she wanted to save that for her own book. (Which, if that's so, don't talk to Shatner about that stuff, Nichelle. He can't use what you don't give him.) And she
REALLY didn't like a bit where Shatner and Kreski quoted her out of context by saying that GR's "appetite" was "voracious," with all the sexual connotations that that implies. What Nichols said she
actually said was that GR had a voracious appetite for
life -- Which, yeah, that's quite a different thing.
I have a feeling that some of that might have been Chris Kreski's influence, as he also co-wrote Barry Williams'
Growing Up Brady, which had a similar focus on salacious details like Barry Williams going on a date with his TV mom Florence Henderson, and the teen romances among the cast playing the Brady kids.
Barrett's statement was much more general, along the lines of (again, IIRC): "Bill's book should be in the fiction aisle, it's so full of baloney."
Sorry I can't give you more details, but that's all I can recall right now. If you're researching this stuff, I hope it's of some help to you.