In contrast to the other reviewers on this site, I believe that this book is an excellent preparation for the BMAT exam. True, it doesn't explain everything that could be asked, or tell you how to pass, but what is does do is give you a good overview of the exam, and practise questions for it.
If you are looking for a book to teach you everything you need to know, you are in the wrong place, you should be looking for GCSE biology, chemistry, physics books. The essay of the BMAT I would say is hard to revise for, you simply need to discuss what is being said. Further, Universities weight it far less than the other sections. So there is less point trying to find a book telling you how to write an essay.
Perhaps i'm the exception to the rule, but I found this book to be more helpful than the other 2 (3rd party) books that I bought on the matter. I strongly believe that the best revision is not to look for a "magic book" but simply to learn the GCSE science syllabus well, and use practise questions from this book and from past papers off the BMAT website to help you understand what things come up (mechanics is quite frequent If I recall). Once I was in the BMAT exam, I couldn't remember anything that the "Pass the BMAT" books said, but the overall knowledge of the exam, revision of GCSE science, and this books and on lines past questions enabled me to do well