Tutorial books

The tutorial books teach you the content you'll need for the exams, though will have some questions to test your learning.

The workbooks are purely question based and test your understanding of what you learned in the tutorials. In addition to more questions to try, they'll have practice assessments which will help familiarise you with the layout of the real exams.

So in answer to your question, you should definitely study the tutorial books in order to have the theory required to perform effectively in the workbooks.