There are only 30 easy multiple choice questions based on basic ATPL. All current jet drivers should know answers. There is no need to go and spend weeks reading various books.
Aptitude tests include around 6 modules and you can not prepare for it. It tests your cognitive skills, reaction time, coordination, reasoning, math and so on.
Group excercises are easy - evaluate the ability to work as a member of an efficient team.
Around 55% of candidates fail the sim check and at the end another 20% fail the psych evaluation. Most of the psych questions are pathetic and irrelevant but your answer does count. Let's say that a candidate is single and his/her parents are dead. Sample question: Do you hate your mother or do you argue with your wife? I think that one company in Australia (maybe VOZ) started using similar psych tests untill they realised that some of the best drivers in the industry were turned away as psych. unfit.