"The Mystery of Consciousness" is simply an expansion and revision of a series of book reviews from the mid 90s. Searle has added a first and last chapter in which he expounds his own views and included the written responses of a couple of the authors to his original reviews. Essentially then, the book is a work of criticism with a dash of the author's own views.
The book is well-written and interesting. Searle can tear an argument into its constituent pieces, summarize it and raise objections as clearly as anyone. It also provides an excellent survey of some important authors on the subject: Crick, Penrose, Dennett, etc. However, as usual with unsolved philosophical problems, it is far easier to tear down the arguments of others than to make a clear, correct argument yourself. Further, it becomes obvious that the authors (including Searle) are talking past each other...using the same words with different meanings.
The problem is illustrated at the very beginning. On page 5, Searle writes:
"One issue can be dealt with swiftly. There is a problem that...does not seem very serious to me, and that is the problem of defining "consciousness" .... if we distinguish between analytic definitions, which aim to analyze the underlying essence of a phenomenon, and common-sense definitions .... it does not seem to me at all difficult to give a common-sense definition of the term: 'consciousness' refers to those states of sentience and awareness that typically begin when we awake from a dreamless sleep and continue until we go to sleep again"
And hence come many difficulties, because the other authors Searle is studying are not all using this definition. They are not all even using their own common-sense definitions but may be using analytic definitions. Thus, Searle's comments like "consciousness is irreducible" are obvious to him, using his exact definition, but not all obvious if consciousness is defined some other way. Further, science and mathematics are littered with common-sense definitions that turned out to be useless or wrong, for example, the assumption that light consisted of waves and matter of particles, and the absolute monistic nature of each as one or the other. His mantra that "Consciousness is a biological phenomenon like digestion or photosynthesis" is tautological if we are referring to his intuitive definition, but flatly false if defined in other ways.
Thus the weakest part of this book: the exchanges between Searle and Dennett and between Searle and Chalmers. In the Searle/Dennett debate, both end up shouting past each other, pointing out the absurdity of the other's positions and the obviousness of their own, because they are using different definitions of not only "consciousness" but "mind", "qualia", "artificial intelligence" and even such basic terms as "subjective" and "objective". The Chalmers conversation is a little less acrimonious, but just as unsatisfactory...Chalmers at least comes across as more of a gentleman than Dennett or Searle.
The final chapter, Searle's summary of his own position, is excellent. It is more balanced and self-critical than his remarks in the original reviews and offers an excellent Q&A that anticipates the objections to his views and answers them. Nonetheless, as Searle himself recognizes, the book leaves us mostly with questions, and we may eventually find even the questions are wrong.