I would recommend:
The AB Guide to music theory parts 1 + 2
http://www.amazon.co.uk/exec/obidos/ASIN/1854724460/ref=sr_aps_books_1_1/202-3205036-5644648
http://www.amazon.co.uk/exec/obidos/ASIN/1854724479/ref=sr_aps_books_1_2/202-3205036-5644648
I use these books all the time to help with my college course, and the classes are based around whats in the bokos too.
Book 1 covers everything up to grade 5 theory, book 2 covers 5 - 8 I think.
So beginners will definately only need to buy book 1.
Just a suggestion :)
- J