The first one is written by the exam board, so if it's in there then you're good to go. Other books are alright, but occasionally you can find things explained in more/less detail or worded differently, that can catch you out.
We had copies of the first book at college, the exam board endorsed one, and I think it's fairly reasonable. They also do a much shorter revision version, I believe, which is handy for condensing it down when you're near to exams.