Sorry to dissagree with you Ham Phisted but I found them invaluable. Each to their own!
I spent about 2-3 days going through each book. You do not need to learn every question and can skip the areas you understand. I only discovered these books (some had not been written) halfway through my exams. In those subjects where I used the books (my weaker subjects) I got over 90%. The results speak for themselves.