Agreed with 800.
get both books. taitys book is. i found the basis for the best results. while the Aviation centre one covers the same with extra stuff in detail that bob does not cover. both are invaluble in getting the best results first time.
i did my IREX with bob himself at his archerfield school. what a legend! the exam is the hardest of all exams to do and with both books on hand i passed first go.
study tips.
read bobs first then cross reference with the other. I found this to be best for me.
Good Luck and study hard
BP