...I have to disagree on the reasoning test being easy.
http://www.iqtest.dk/main.swf - perfect example of the Raven's progressive matrices which you are tested on in the reasoning test. Not as easy as it might seem, if you get 90%+ on that test consider yourself extremely clever.
Studying for the interview goes far beyond knowing the JKI booklet inside and out. Supplemental knowledge is vital for this, especially information on Hong Kong, CX, and AFT. They will ask you technical questions to the limits of your knowledge, and then a little bit further. They look to see that you have the knowledge that you ought to possess considering your aviation experience, and that you have done even more research (if you were really interested in flying you wouldn't just learn the bare minimum but you would read up on more advanced material). Furthermore you will be asked questions that you do not know the answer to, how you respond to such questions is vital, can you work out the answer by piecing together what you do know?
Exude confidence in your interview, if you have prepared yourself sufficiently this will come naturally, walking in to the interview you should feel ready to answer anything they throw at you.