Falk’s motivations for creating this siddur are outlined both at the beginning of this book, and in greater depth at the conclusion. She cites a quote from Arthur Green, a luminary in the world of Jewish Renewal and non-dualistic Judaism. Green says that even though he believes that there is no such entity as a God separable from the world or people or the things in it, he still uses the language of liturgy that presumes such a separation of objects. Falk admires Green's work, but finds this a strange position to take.
So, the reader should keep this in mind when using The Book of Blessings. It has little resemblance to many siddurim out there. Even the siddur of the Reconstructionist movement is not as bold at replacing the formulas for blessings and most aspects of liturgical language found in traditional prayer books which presume a personal God and a personal supplicant.
So, this siddur will speak to many people. Other people will read it and see it as fundamentally un-Jewish, despite the extensive Hebrew. The siddur you want is for you to decide. In our world, we are Jews by choice, and with that in mind, we get to choose our prayers.