Leo and Catherine are wonderful! Okay so maybe I don't love them as much as the previous two book but I do love them. They have this witty banter between them that is fun and refreshing. It is wonderful to see things from Catherine's perspective and you realize quickly that one of the reason Beatrix's wild nature and Poppy's need to spew fact and information were never curtailed, in order to secure a husband, was because Cam said no and because Catherine loved them for who they were. It is obvious that she loves the Hathaways like they are her own family. 
 Leo has had a rough journey and one that is plausible and understandable. He held the woman he loved in his arms as she died and then desired to die himself. Merripen didn't let him and instead nursed him through his scarlet fever. Leo didn't appreciate it at the time and turned to every vice he could to drown his sorrows and himself. In the first book, Amelia and Cam come to Leo's rescue and Cam helps Leo let go of his past love (who was haunting him because he wouldn't let go). Leo then proceeded to gradually get better though his zest for life seemed missing. He found it again while in France with Win while she was at the clinic recovering. 
 Upon returning to the Hathaway fold, Leo stumble upon Catherine Marks and is forever change. She awakens him like no one has in all the years since he's lost Laura. 
 The best thing is that they both seem to combust the moment they are together. And one of the best things is Dodger's (Beatrix's ferret) love of Catherine. He torments her only because she says she despises him only she seems to tolerate his presence and attention quite well. 
 Catherine's past is a harsh one, much like Harry's but Catherine comes to terms with it. Catherine's problem isn't realizing that she wants Leo or wants to be part of the Hathaway family, but rather the inability to take what she wants most. 
 Great story and great series!