Incoming wall of text no one cares about now that I’ve finally completed all four routes:
M’s route stood out as the most solid one. Well paced and satisfying. It was always one of my two favorites but I had some issues in the past with some of their lines occasionally coming off as cringey rather than sexy. Luckily, past the demo, these kind of lines decreased in frequency, as the relationship deepened, while still not sacrificing the sensual side of the romance.
Also all ROs have their own ongoing subplots but the mystery surrounding the crystal is the one that has me the most curious and it’s interesting to see that the detective gets headaches from their pheromones even when not on M’s route, while being able to alleviate M’s painful sensory issues, on the other hand, is romance exclusive 
A’s progressed further than I expected going in. I did imagine there would be a kiss but I thought that, emotionally, the relationship would still be stuck in the same place. Glad to see I was wrong and that the kiss wasn’t followed by the usual moment of denial and excuses. Looks like the loop their romantic scenes have been trapped in has finally been broken!
Short of actually getting together (which was obviously not gonna happen in this book), this is the biggest turning point that could’ve happened. Now everything’s out in the open and I’m excited to see what shape their future interactions will take. Already in this book A was much more relaxed and confident around the MC and I enjoyed seeing more of their character’s quiet, well dosed, sense of humor.
I was, however, left unconvinced by their backstory and expected more. We don’t know yet how they came to be a vampire so I hope that’s not all there is to it and that future revelations about their past will do more to justify their present day beliefs and attitudes towards humans and relationships.
As for N, I’m pleased to say I didn’t find their romance a complete snoozefest this time around. It’s still not the most exciting route imo but I can kind of see some allure in the character now and while we’re still far away from getting a full picture of their background, I do love sea mysteries.
Then there’s F who still leaves me feeling like there’s absolutely nothing going on in their route, just as I did in the previous two books.
Not an issue though. Enjoying two and half romances in a game of four is enough.
As for the plot stuff:
I had two theories based on the demo and both were wrong lol
One being that the villain would be someone relevant to the detective’s life (not a character that had already appeared but at least someone whose existence was suggested). I thought this could be the case due to there being an intermediary villain, Sin, and the fact that in the demo we saw the real villain only through his eyes and their name wasn’t mentioned. This made me suspicious in regards to their identity but it was just some rando oh well lol
I also overstimated the drama that would ensue from the antagonists deciding to kidnap someone close to the MC. I thought it’d be the RO (causing a role reversal of having the detective being the one coming to the rescue) or perhaps Rebecca. Vieno/Tapeesa didn’t even cross my mind cause they only had one scene with the detective prior to the demo… two before the kidnapping. And indeed them being among the hostages didn’t seem to make much of a difference. UB+Rebecca and MC would’ve intervened regardless and it’s not like emotionally the detective was hit particularly hard by Vieno/Taapesa being one of the many victims.
One thing I appreciated was having more freedom in regards on how to navigate missions, even if at times the way things were handled was a bit simplistic. I’m guessing this is something we’ll see more of in the future.
Lastly, as others in this thread have already pointed out, there should’ve been a million ways to avoid the blood drive and while I could’ve, maybe, sort of, understood forcibly making it a big issue for story purposes, I also felt like narratively it added nothing of value.
Oh and one little sidenote: the topic of the ROs finding it difficult to handle the MC’s blood was finally brought up. We’re one step closer to the best scene of every vampire romance y’all: sexy biting.
That’s really what I’m mainly here for, not gonna lie.