Because of one section. I'll explain it after the jump, to spare anyone who might become uncomfortable by it. Also, spoilers. Suffice to say, however, I almost quit reading the book for good.
So basically, Honor, her two remaining ships, and what was left of the Grayson's Navy (which i believe was a pair of light cruisers, a few destroyers and some LACs - Light Attack Craft, which is sort of like one of those missile boats that Middle Eastern countries tend to invest in - move in to attack a hidden Masadan base and the remaining forces they had in the Yeltsin Star System. Prior to and after the battle, it was hinted by the Havenite commander* of the lead enemy vessel that the Masadans stationed at the base had done something that they found disturbing. As it turns out, the Masadans had captured some survivors from the Manticoran destroyer HMS Madrigal and shipped them off to the Blackbird Base. During the assault on the base, it was again insinuated that the Masadans had done something bad to the prisoners.
Just to cut to the chase, it's revealed that the base commander had allowed his men to beat and gang rape - repeatedly - the female survivors of the Madrigal's crew. You see, the Masadans, aside from being religious fanatics (they make ours, regardless of religion, look like atheists) with a misogynistic bent so extreme, even real world misogynists would be aghast.
Needless to say, I was horrified and just disgusted. David Weber wasn't trying to glorify rape and he certainly wasn't using it lightly, but the shock of it hit me like a sledgehammer. I soldiered on, however, and I'm closing in on finishing it.
*The People's Republic of Haven, the Star Kingdom of Manticore's primary rival, was attempting to help Masada "reclaim" Grayson in order to get basing rights from the religious nuts and put themselves into a better position to attack Manticore.