I've been a big fan of all of the Clare Darcy books I've read until this one. It's the story of an impetuous rake and an extremely gullible ingenue who end up in some actiony situations together before they get engaged. After this, their relationship is all jealousy and fighting until literally the last two pages. I liked the set-up of a marriage of convenience and their dynamic early on. However, this is a book that gets overtaken by ridiculous protracted scheming in the last act, where one unlikable character decides to take evil pills and become a crazy villain for no reason. And the main characters just go along with the scheming without a second of doubt.
I was very disappointed in Darcy's plotting in the second half. Usually, she's good at marrying action/conflict and romance, but not in this one. It's the kind of book with very little communication between the couple after the inciting incident. Rather than romance, Darcy centers danger and action from about 40% to 99% through the book. And the scenario leading to this conflict is absolutely braindead.
In short, too much of the main characters being uncommunicative idiots, too much of them jumping headfirst into schemes, too much forced conflict, and too little actual romance. By the end of this book, I seriously started agreeing with all the supporting characters who said that their marriage was a bad idea. If your romance book makes you question the basic premise of their romance, what are you even doing?