Let me start by saying I think Kate Quinn is one of the strongest writers in historical fiction today. I adored her Rome books and found the fist book in the Borgias series equally well-written. She does a great job integrating well-known historical figures with characters of her own creation and not making it seem manipulative or over-the-top (I thought the plot twist toward the end of Daughters of Rome was a perfect example of Quinn's great storytelling skill). 
 The first half of The Lion and the Rose did a nice job of carrying over the themes and characterizations from Book 1. However, around the midpoint of the book (view spoiler)[(the confrontation between Leonello and the killer he's been hunting for the last book and a half) (hide spoiler)], I found it went a bit downhill and the flaws I could otherwise ignore were more exposed. Most of these flaws pertain to the Borgia family and how their portrayals devolved as the story went along, but I also found this book's "twist" (view spoiler)[involving Giulia and Leonello's relationship (hide spoiler)] came completely out of the blue and didn't reflect the characterization that had been so strongly built up over the previous 400+ pages. The ending felt a little too abrupt and nicely tied up (and actually, a little too modern as well). All 3 main characters were so fascinating and complex that I thought they deserved a more interesting and fitting conclusion to their respective journeys. 
 All things said, this is a well-written and entertaining foray into Renaissance Italy and the world of the Borgias. I just can't help but wonder if this series might have been better served as a trilogy so that the second half plotting and characterizations just weren't so jarring.