In my humble opinion, the study materials
for these exams are a very valuable resource ...
... and the exams, themselves, are not
Testing companies go to their own internal staff as well as to knowledgeable people from the outside world to put together a course-of-study that will determine both
the content of the test (which they sell ...) and the far-more-lucrative study materials, which they also sell. The course of study is designed to be representative of what actual people, actually on the job from day to day, will encounter, and what they will need to know. At the end of the day, whether you buy a pretty piece of paper to hang after your name or not, these are
things that you need
to know. Exam study guides are a very concentrated and targeted source of information to that end.
But don't study those things in the same way that you learned to study things at school. When you "pass the test," it's not over. "Passing the test," or even taking
it, is really not the point. "Getting a diploma," also, is not
. Actually learning the material and acquiring the skill is the only real goal you have. (You can certainly get a piece of paper and know nothing ... they will sell it to you anyway.) Unlike school
... you actually have to come away from the experience having learned
I have several (somewhat older, now) exam-prep guides in my library and I do refer to them from time to time. You will find not only descriptions of a procedure (which may of course have become outdated), but of the theory behind it (which of course will not). In the real world, you have to have a sometimes-intuitive grasp of why
something is happening in order to conclude what
must be done about it.