I was hoping Eleanor keeps away from Hart or, as I call him, "heartless" for another ten years or more; of all the brothers, he was the "sick" one. 
 In The Madness of Lord Ian Mackenzie, I found Hart McKenzie to be a despicable human being. He manipulated his brothers and others for his own selfish gain. He treated his mistress, his wife, various prostitutes he employed in a separate house, and his sister in-laws like dirt. He had no regard for anyone. This is a man who beds and asphyxiates a prostitute right after Ian had sex with her by his explicit orders to find out if she was planning to blackmail him. 
 He protected his mistress even when he found out she was a murderer and almost killed his sister in law. He mourned for her in ways he never mourned for his wife or new born son and never really apologized to Beth or Ian. 
 In book 4 we learn more about his mistress. We learn he knew well about her jealousy and all she would do to keep him. He should have been very aware of what really took place in book 1. This is a woman who took it upon herself to go and let Eleanor know about his other house and what was going on in there. She destroyed his betrothal to Eleanor, the only woman he says he loved. What did he do? He gave the house to his mistress and as soon as his wife and newborn son were dead, he started going back. He treated Angela better than his wife or Eleanor. Angela, who would hire a virgin maid, lock her up, threaten her and serve her on a silver platter to Hart so he can enjoy deflowering her. While Angela, his mistress, was living the lap of luxury and wearing the most expensive clothing and jewels, Eleanor was living in poverty and destitution. If he really loved and cared for her, he would have purchased her father's scientific books anonymously. It is my belief that he wanted to destroy her as he said when she gave him back the engagement ring and that he enjoyed knowing she was poor and dependent upon the aid and generosity of people who used to work for her father. Why? Because he was a cruel, manipulate human being who played with and discarded people, including his own brothers. What I deducted from these 4 books was that he loved and appreciated others that were as despicable, heartless and manipulative as him - no wonder he mourned Angela's death. He might disagree but by all his actions he showed us Angela was the only woman he thoroughly loved. He cared for her, protected her, accepted her as who she was with all her faults. 
 In book 4 we are to believe the sexual extremes that he didn't want to talk about were nothing but taking nude pictures and some very mild games in which he likes to tie women up. I don't think so! I've read the first book and watched through Ian's eyes what he enjoyed doing in a bedroom with open door and Ian has impeccable memory. 
 I understand lately a lot of authors are introducing mild BDSM in their books because they see the interest and book sell and what I think is because they don't want to repeat the sex scenes from other books in the series, but trying to redeem a despicable character by saying he is who he is because he needs to control and dominate in and out of a bedroom is utter non-sense.