Grove (Maths in Focus) is good for getting a handle on the basic problems.
Fitzpatrick (the yellow one) is much more detailed and has harder problems. This is usually found to be one of the best study aids (for extra questions etc).
Cambridge (with the Sydney Town Hall Organ) is another good one to have on the side. The problems lean to the difficult, excellent preparation for the exams.
One you can afford to ignore is Excel. They write summaries more than anything else, and you need more than that. A thorough understanding is the end goal, something Excel simply doesn't deliver.
If you're looking at reference, however, their pocket book is a good investment. At around $12 you have a little book you can take on the train with the "bare minimum" you need to know and understand. It has all the formulae, with brief explanations and worked sample questions, as well as vital definitions and "exam tricks" you would do well to memorise. Take a look at it. If learning by rote is your style then this will save you some trouble, but remember that you MUST do many, many practice questions for even a hope of band six.