I didn't know the man personally, but I can tell you all this. Beware of books that come out after someone's death claiming to "the truth" about what kind of person they are. Any accusations about someone's character should be made when the person is alive and can defend those accusations.
That's fine in theory, but when retaliation for whistleblowing is commonplace (and going by the way laws are being passed even now, it seems like whistleblowing is now considered to illegal by most Republicans and several states where you cannot go undercover to record the mistreatment of animals), it is damned hard to speak out.
GR threatened to blacklist Ellison if he insisted on keeping his pseudonym on CITY, and his attorney in later years was positively crazed, as has been attested to by pretty much everybody who had dealings with them.
It wasn't till after the death of GR and his attorney that Gerrold finally managed to settle (for a pittance, sadly) for some money over being screwed out of co-creator credit on TNG.