My 13yo son and I have discovered the Percy Jackson books. One was made into a movie recently but my 13yo was disgusted they changed it (that's my boy!). They would be suitable from 9/10 up I think. I've really enjoyed the first two and we borrowed the third one from the library and will now have to fight over it Good characters, action (which isn't usually my scene) and humour.

http://www.percyjackson.co.uk/site/pj_books.php

I have seen the books at Kmart too.

Tomorrow When the War Began series by John Marsden.

Great read and also used in school a lot - i had already read it when we did it at school. It was the one book that got everyone in my class reading - even the boys.