As the title says not all exams are covered so you will have to do some work on your own rather than memorizing the answers, yeah I know horrible thought. I used to teach this subject for 8+ years as well as 25+ of industrial experience and have seen the dumbing down of the qualification, let alone what they turn out of schools. To redress this issue, to their credit, City & Guilds have tried to tighten up the very loose edges of the 6129 by bringing in the 6189, although in my opinion not tight enough. In doing so they put some rather obscure technical questions that are not really relevant to the occupational plumber but needed all the same to pass the exams. This is why I like this book because it requires the prospective student to actually do some revision and learn the fundamental principles of the science of plumbing and that is a good thing. Why should I be so critical? Simple really as more people die each year from bad water than they do over a gas issue, be it CO poisoning or explosion. LEARN YOUR SUBJECT!!!