This book mentioned is good in the way it shows quite well (at least I hope so) the scope of the exam, and is very, very concise - which is good thing, if you know everything, and just want to refresh your knowledge, but it's difficult to learn from it, if you don't know something. In such case it's more like a reference, and you need to find some other materials (for most of the subjects you can find it's on-line). Therefore it does exactly what it promises - it guides you in your study
About whizlab, I've read here that it's not completely representative of what you will find on exam, but as I haven't taken one yet, I cannot say anything about this. Some impressions I have so far:
- it's much worse than their Java Programmer Simulator - I remember that big advantage of their
SCJP Simulator were great explanations of each topic, with links for further study etc. I learned almost exclusively from their simulator, reading the answers and reaching for external sources in few cases that it was necessary. Forget about this in SCEA, explanations are very vague, and at best you will understand why did they select this choice over some other.
- now it works only on-line, and requires you to have good and stable connection all the time, otherwise it's unusable. My current Internet connection sometimes breaks, and with such fact their AJAX engine cannot cope at all (no refresh button etc.).
Anyhow, I think it's useful to do at least some tests, as it requires specific way of thinking (and alertness

), and it's better to get used to it doing some stupid errors on mock tests, than on actual exam.
Bear in mind that I haven't yet taken exam, those are my thoughts from preparation so far.