Castlevania and Empire of the Vampire would both be accurate comparisons to the vibes of this book, in my opinion.
Albeit that Jay Kristoff's writing tries very hard to be edgy and "historical", as this one does not.
I found myself really thrown off by the sudden use of present-day slang though. That one time the main character actually said "Sounds like a you problem" made me laugh out loud. And not in a good way. Other times though, there were lines I actually liked the writing of.

The author clearly tried to craft an original world with her own version of vampire lore, origins and mystery. This didn't fully land for me though, as the main focus of the story was a bit lost to me most of the time. In theory, I should've enjoyed the romance or the mysteries and battles that were happening. I just found myself not caring at all, but still slightly entertaining because how far the author dared to go with the gore and mature detail of the story.

All in all, I found myself quite conflicted about this book. The ending "reveal" was, as all the other reveals, something I have read multiple times before, so I find myself not intrigued enough to continue with the second book (I also have heard it's really bad so that gives me all the more reason not to pick it up).
As a book that I read while mostly turning my brain off, it was an okay form of entertainment in the end, I suppose.