Exactly what the subject header says, folks. If you're looking for a history lesson, despite what others have said, this isn't a good start. What you've heard about the Middle Ages is wrong with a capital "W."
In the case of what really went on in the "Medieval" ages, read Regine Pernoud's "Those Terrible Middle Ages" as a starter, as she was an actual archivist, scholar, and all around intelligent lady on the subject of the real middle ages and what they were really like.
TLDR; If the middle ages really were that bad, we'd never have made it to today.
Now, onto more important things. Such as the question "Is Berserk entertaining?"
The answer, in my opinion, is yes, but my opinion is wavering. But let me explain why I feel this way in further detail below.
You see, when I first started the series, I thought it would be a simple Guts vs. The World with that world being a dark, cruel, and overall not nice place to live in. And, for the first 13 books, that's what I got, and it was good. Real good. Not a thinking man's story, just pure unadulterated entertainment and, despite it's flaws it was truly a great romp. Suffice it to say, as I saw how long it took to get where I'd come in at (I think I came in around the mid 200s) I was concerned that it had started before I was born, and wouldn't end until long after I was dead. I have yet to be proven wrong on this, and that knowledge frightens me greatly.
But as of late this view is slowly eroding as, with each chapter that comes out (beginning with the Berserker Armor and the Loli-Witch, I'd hazard a guess) it feels less and less original and more and more like it's falling into normal fantasy which I'm greatly concerned over. Perhaps the guy just started getting too depressed and wanted to liven things up, but if that's the case then he went about it the wrong way. It feels like, with each successive chapter since the world acquired this weird full on fantasy approach that it's beginning to look less like Berserk and more like... well, that's just it. I don't know what it looks like, and that's a problem since it's obviously not the Berserk I entered into with joy and excitement all those years ago.
Some of my issues are with the party: Puck should be less comic relief; Ishidro just feels... gleh; Serpico and Farnese could have been salvageable if, perhaps, they'd been just as screwed up and actually did get incestuous (I can't believe I'm advocating this... dear me) as the rest of the story is screwed up just as bad, if not worse; and Isma... Isma is actually one of the few additions I have no problem with, actually, except that I wish she'd been around during the darker chapters, honestly.
So my opinion is that I hope it gets darker from this point (chapter 333), and with recent events Miura seems to hint at it, but I honestly have my doubts, and these doubts are very big doubts indeed that it will ever match it's former greatness.
At the end of the day, a story's worth is based solely on how entertaining it is, and so I'd say this story has, in it's earlier chapters, a lot of worth (beyond the ratings available to us here) and, perhaps, greater worth ahead. But as of current chapters? Well, not as much worth as I wished it had, honestly.
Hopefully this helps, folks. And here's to hoping of better things ahead.