I am suprised nobody has answered this yet.
The JAA IR must be done at a professional flight training organisation and these use certain training materials, so this is what you need to get because the exam questions will be constructed on the assumption you have studied from those materials.
The JAA question bank is also now available, so you can check you have got the right answers! Somebody told me that the place he studied at let him have access to the question bank for something like £50 for 3 months.
You will find resources at
PPL/IR Europe.