Glad to read this one, even if it made me cry a couple times. A scientist/countess (of course, rich) can't take credit for her (of course, ground-breaking) research in genetics so uses an old friend as a beard. Finally he tires of it, though he never tires of her, and they must come to a different agreement. I enjoyed how both Sebastian and Violet grow during the story and how realistically the science and discovery are portrayed. She doesn't come up with answers out of thin air, but after years of painstaking research and with the help of others, just like real science.
But the part that hit me (happily) in the gut was the assumption that Violet deserves a happy-ever-after, though she is one of the prickliest, hardest, smartest heroines I've read in a romance. She doesn't change personality to "win" her man; he's already won over. The person she needs to win over is herself. I know many sharp-edged, brittle, single-minded, wonderful people in life, and I believe they and all of us deserve happiness. But in romance it often seems that the woman has to meet a "niceness" standard, or she's the villain. Not here, refreshingly. I hope in the future we can write characters who are prickly just because they are and not because of some horrid things in their past, but this is a good start.
I can let go my tiny issues with plot and pacing, but a backstory reveal late in the story felt mechanical (and murderous) and left a bad taste in my mouth. It didn't feel necessary to me, and cast a yet earlier death in a suspicious light. But it didn't take me out of the moments in the story, especially the scenes where Sebastian discusses variation in violets and later when they parse the "human species," rakes. Very well done.