The AB guide to Music Theory Part 1 & Part 2 books and even his theory books 'Music in practice Grade1-5'.
I would definitely get this book & also Part 1 as well - but you may find that you already know all the things in Part 1 but there were a lot of words i didn't know in there.
I would definitely recommend his theory books (Music in Practice Grade 1 up to G5) I wouldnt get Grade 6-8 though - the authors of those are Peter Aston & Julian webb and the change of author really does show as the book lacks in so many areas and the things they fail to cover - which you must know for the exam - is astonishing!
If you're doing theory exams I would also recommend you get the 'Theory workbooks' and get past papers - they'll help you alot.
But back to these books - which me & my teacher refer to as the pink and blue book - are great. You should definitely get them.
But in getting this book (P2)it assumes you know all the things covered in the pink - part 1 book eg. the basic staff crotchets, bars, fermatas(pauses)etc. to the more advanced things like feminine endings, double phrasing, slurs, turns and trills etc..