I read this one and the next one together (as is my wont with these multi-part VHD books) and liked the first one better. The main antagonist, Valcua, is more like a final boss in that we don't actually get to see him and his capabilities until much later. Instead, D and his temporary compatriots have to fight through several of the big bad's retainers and all they have to offer, and this is good stuff.
Then we get into the Ultimate Noble, and it feels like it goes a little downhill from there. There's a new character who is made of questions and no real answers are forthcoming. Valcua sends D through this gauntlet of challenges to gauge his strength, and it comes back over and over more than can be measured. Then there's the final confrontation, which got kind of weird.
But the weird isn't the problem. It's how entirely OP Vampire Hunter D is, that's the problem. Throughout most of the adventures, D is just a hair better than he needs to be, just a shade better than the antagonists, which is okay. But this Ultimate Noble is ridiculously overpowered, and therefore, so is D. And that's the issue. Why was the whole front half such a struggle if D is so everything? And don't think about the preceding fifteen books with this power level, right?
It's the Superman problem, but with D. It really left me dismayed with future adventures. I mean, I'll read the next one, but... eh.