You have to find the balance between learning the important points on the syllabus and learning the answers to the questions.
A lot of people know the answers to the specific questions, but when you probe their knowledge you find the foundation is missing.
The OAA's books may be overwhelming at first, but the more you know the better, you never know when one day that little bit of extra knowledge could help you out.
In terms of answering the questions, the PPL Confuser is years out of date, the PPL perfecter is the best way to go.