This is fascinatingly ... flawed.
There's so much I admire about this book, the heroine is great, the writing is smooth, it's fucking bold for taking histrom is a rarely-taken direction. I loved the fact that sex-work isn't shamed, I loved that the heroine got to be passionate (both sexually and in her life in general) and I loved the fact that the hero's relationship with his mistress (in the BDSM sense here) was always treated respectfully.
I think the things that didn't work for me were sort of ... first book things? I mean, there's a LOT going on here, between Poppy's botanicals, the hero's grief, the hero's kink, this "one steps forward two steps back" dynamic between the hero and the heroine, where it feels like they're just coming to a better understanding of each other then NOPE. I'm not the biggest fan of the "one steps forward, two steps back" thing in general - although I think it can work, as long as it is carefully structured. For this book, it felt to me as though they'd figure something out in one chapter, and then immediately find another to cause tension in the next, and the cumulative impact of that (again, to me) was their relationship progressed somewhat unevenly, and slightly randomly. On top of which, I'm inclined to think there's too much happening - so some things feel less resolved than others, or else appear without warning like your latest friend at your birthday party.
I also - and this is largely personal - wasn't super convinced by the way the kink strand of the plot was resolved. Firstly, the heroine finds out the hero is kinky because she literally pursues him the brothel where he gets his kink on and sees the kink taking place: while I'm super glad this wasn't handled in a demeaning way to any participant and the heroine isn't awful about it, I generally prefer characters to learn about each other because the other person has chosen to share. That always feel more meaningful to me than, "oh, I accidentally discovered this about you" because I'm obsessed with the inherent romance of ... um ... what we choose to share with the people we care about, and how difficult that is, wanting to be loved and be open, but terrified of being ugly and rejected.
And so part of me is left wondering ... if Poppy hadn't literally barged in on him, would Westmead ever have got his balls together and told her? And what does it say about the future their relationship that he didn't?
(Err, I am muttering about this, because I cared about them, and cared about their relationship - I don't get worried about the lasting potential of fictional peoples' relationships unless I'm invested. Also it's strongly a personal taste thing, and I'm not against "I worked it out" in all cases, it's just Westmead is so closed down emotionally-speaking, and Poppy is amazing, so I wanted him to just make the leap and fucking trust her, you know?)
It also feels like the kink strand is fully resolved with one kinky sex scene that came, I think, in the last 20% of the book? Maybe even the last 10% of the book. Again, I should probably emphasise that I'm not demanding more hawt submissive duke action (although submissive duke, in itself, is such a fucking gorgeous concept I will take as much of it as I can get) but I feel if that a sexual element is entwined with one of your emotional conflicts you need to give it as much on page time and development as, for example, the dude's dead wife.
So, for me, I think I needed less emotional back and forth, for the kink thing to come out earlier, and for it be resolved more comprehensively. Also I vaguely wish he hadn't got kinky because his wife had corked it.
All of which said, I would take a fascinatingly flawed book over a well put together mediocre book any goddamn day of the week.