I'm preparing for the CISSP exam, and I have access to the free testbank that come with the above mentioned book, there are 1320 questions.
Can I trust the assessment on my proficiency, just by doing this lot of questions ? is this enough ?
It's a good indication of how you're doing knowledge wise - but in honesty I would say it's not a great indication of the types of questions you'll face in the exam.
If you're doing the Sybex online questions and smashing them, say 85-90% then (as long as you're not getting them right from memory - rather getting them right because you understand the concept / subject), I'd personally say you're ready... Others may have other opinions. I did see threads here before i took the exam of people complaining the exam is nothing like the Sybex questions etc, and that's kinda true - i would say they are a bit harder in the exam in that (certainly in some examples) more than one of the answers would be correct, you have to pick the BEST. Think as a manager when you choose which is best...
Good luck - and i'm certain others will offer feedback here also.
Regardless of the test bank you are using, be sure you understand WHY the correct answer was the correct answer.
Another source for questions is the site cccure. Also, ISC2 has practice question materials. Good to check them our as well.
Over the years I find candidate often confuse quiz books, knowledge banks and "testbanks" with outright brain dumps. Wanting as marginally close to the actual questions, if not the questions themselves to be layed out in easily memorized formats instead of learning the material as a whole. This leads to a false sense of security and devalues the overall need to pass an exam for the sake of passing an exam.
What your supposed to be doing is learning all the concepts and materials related to the exam so you become a valuable practitioner backed by the assurance of passing an exam. In other words, the exam is not the ends to means but the means to an end.
If our goal was to simply train people in passing a number of questions on an exam our outcome would be lots of "exam passers" or certified empty exams holders with no real knowledge. Unfortunately, the latter only hurts those practitioners who fully understand the required concepts in the real world making the exam itself less important than the knowledge carried within.
You really need to ask yourself do you want to work and rely on people who know what they are doing or people who can simply pass an exam? I can study over a weekend and pass any IT related exam but does having that type of credential really help my organization?
Learn and know the concepts and the quizzes and test banks will become less important than before. Yes, I say things that may people find uncomfortable. No apologies.