Initial reaction is that it's not my favorite story of Cullinan's, but it's not her weakest in my opinion either. Not a glowing remark from me, but it is the initial reaction. 
 I don't generally like reading stories set in this general time period, but I think this one did well for me personally because it didn't feel like she was trying too hard with the historical ambiance. It has it without being overbearing about it. There are some historical fiction stories which feel like the author was trying way too hard to add ambiance details and get terminology right. (If I have any complaint in this regard, the plant biology rather bored me in a few places, but that really has nothing to do with it being a historical and more to do with the MC being a botanist.) 
 The main characters both had their own strengths and weaknesses. Both are somewhat broken by memories from their past which are separately related to one's father. Each provides the other with an anchor to help get past their issues, but as is common, sometimes they have to break some more before they can be put back together again. Then they get to confront their demon after they find out he wasn't just a heinous bastard in the past, but he still is. Warning/spoiler: (view spoiler)[He's a pedophile who rapes young boys. At the end, it's found out he's raping his own grandson and eventual heir. (hide spoiler)] 
 In the end, I'm not sure what didn't quite sit right with me. So, gut feeling is 3.5 stars, and I rounded up because it's Heidi Cullinan, which speaks for itself in my mind. Take that for what it's worth.