The fact that this book is as interesting as it is (when, at its essence, it's about one character who reveals not much at all throughout the entire expanse of the novel) is a testament to how well that character is written. But the ensemble cast falls short. The central narrative is almost too long to be a problem and too long to truly allow this book to be great.
This book takes the premise of a door and the woman behind the door, both physically and metaphorically, and slowly unravels it in a way that is satisfying at its core and page-turning. But I do think that it's probably one great support character away from being a truly great book.
This book essentially tries to be Ishiguro's The Remains of the Day, with a character 70% as compelling as the others (Butler) and no support cast as strong. Additionally it has a weaker backstory. I'm not sure if this book is autobiographical in nature and is constrained by reality but the part of me that knows that this book is a work of fiction (a great work of literary fiction at that) struggles to see past these obvious flaws.