This is a provocative and thought-provoking book. I am not aware of competing books. The authors are correct about the book by O'Driscoll and Meagher ("the active management of labor") on which Proactive Support of Labor is based.
It was a classic, but very much the "Dublin experience" and without literature review. In contrast, "Proactive Support of Labor" is strongly supported by clinical evidence from numerous international studies. It should be required reading matter for all birth professionals, obstetricians, midwives and labor room nurses alike.