I have been a filmmaker for over ten years, directing my own films as well as working as an assistant director on numerous indie productions during that period, and I have to say that anyone who is remotely interested in directing and filmmmaking must read this book.
Both from my own experience, and from my close observation of directors I have assisted in the past, there is no doubt that directing actors is the most challenging aspect in the panoply of arduous tasks that await the film director. Some shy away from it, hiding behind the monitor, some stumble through it hoping to arrive at a performance through trial and error, but very, very few actually know how to constructively and efficiently collaborate with actors to create truthful and compelling performances. I think it's because, unlike the creative process of writing a script or generating shot-lists and storyboards, actors are mutable, unpredictable - in a word, human - and somewhat like jazz improvisation, you can't completely plan the performances in a film. Instead, you are forced to observe them develop organically in real time and respond immediately. That's difficult, and the problem is most directors (even seasoned veterans) just don't know how to talk to actors - they don't speak a language that is useful to them. This is where DeKoven's book is immensely valuable and, in my experince, unique.
It provides a real step-by-step approach to learning a new language, which enables the director to give the actor a point of departure for a performance, and allows them to quickly communicate adjustments as that performance evolves. Although the process it describes is very complex, the writin is clear and the approach is very accessible. From the director's preparatory work (what DeKoven calls the throughline), to the on-set collaboration with all creative partners (not just actors), there is no part of a director's craft that will not be enhanced by exposure to this method. This book has filled a gap that I had hitherto been unable to fill in my library of fundamental texts for any filmmaker (you know the rest: Story, Impro etc.), and is a must-have for any filmmaker's toolbox.