This book seems to be addressing two audiences, not necessarily overlapping. It is a tender review of the structure of the Siddur and Jewish prayer, useful for those unfamiliar with it. It is also an informative review of the development of the Siddur over time, and the rationale for the order of its various elements. If either of these is of interest to you, I recommend the book to you. If both are of interest to you, I heartily recommend the book.
Garfiel died in 1987, and must now be forgiven for an error in her book which she is no longer in a position to correct. She writes that the ketubah, the Jewish "marriage certificate," is signed by the bride and groom, among others. In fact, the ketubah need be signed only by two designated witnesses to the wedding.