Like some reviews have said, this book is perfect for bridging the gap between the level of knowledge of the common yogi, even the common non-yogi, and the complex and hard to understand esoteric teachings of kashmir shaivism (for example, quantum physics terminology could be considered esoteric.)
Pratyabhijna is part of kashmir shaivism, and siddha yoga includes kashmir shaivism and vedanta, and it seems to be a fairly unique mixture of the two. Swami Shantananda is fairly in to Siddha yoga to say the least, and has been studying kashmir shaivism for 30 years. A fair number of people seem to agree that pratyabhijna and other philosophies are rather hard to understand without an understanding of the core of kashmir shaivism thought, which is generally considered to be the Shiva Sutras. Swami Shantananda does a fairly good job of explaining most things, mostly from a practical point of view.
I feel that a few key things that he leaves out is that, essentially, your effort is not the means but is meant, what technique you use does not necessarily matter as long as you practice it one-pointedly, that is without initiating any thoughts or daydreaming but absolutely pauselessly. And anger, force, violence, kill god consciousness--destroys your progress. And focusing on one thing in particular, especially when you haven't developed awareness, negates knowledge of everything that is not that one thing. Supreme consciousness is the reality of everything (caitanyamatma); this is the first sutra of the shiva sutras.
Swami Shantananda covers the basic techniques of pratyabhijna and focuses quite a bit, it would seem, on Siddha yoga techniques, and he talks quite a bit about mantras and in the manner he does, gives the impression of reciting mantras aloud. In the case of the shiva sutras, at least in shaktopaya, your mind is essentially the mantra, that your mind contains all the saktis that the mantras contain and that, at least when you have developed enough purity and awareness, your mind truly is a mantra and only then can you use them for the purpose of any given mantra.
This book suffices for pratyabhijna, but I think the shiva sutras by swami lakshmanjoo would be necessary to fully elaborate on the key points listed above, as well as a few other major points, so that you the reader and/or possibly yogi, will have a better understanding of how the geography of awareness is defined, so that you may never go astray.
My less than full star review is mostly due to having not gained much new, as having already thoroughly studied the shiva sutras and the hrdayam, and was looking for the next step essentially (which is probably something very esoteric and ancient) but has opened my eyes to the existance of a yoga group nearby that practices kashmir shaivite philosophy, Siddha yoga. hope at least some of this has helped.