I teach the AQA AS Business Studies course in a secondary school and in my opinion this is by far the best text book to accompany the course. Although not specifically endorsed by AQA, the level of detail and depth that this book goes in to is excellent, and just about right for A-Level. I have also read the Surridge book (very poor - just the same as their old text book except rearranged for the new course), the Stimpson et al book (good, written specfically for AQA however not enough depth), along with various others, and this is without doubt the most comprehensive. My only criticism (and it's not really a criticism) is that at times it gives more information than requested in the AQA syllabus; however the points never come across as confusing or particularly complex.
As a teacher the exercises in the book are great for homeworks and classroom activities too. There are tasks and exam style questions for each chapter of the book. I have ordered a copy for each of my students.