I have recently found this site: Badger Publishing to be a great inspiration...
It's actually targeted at schools - it sells 'book boxes' for particular ages/ abilities etc
If you click through to the detail of each box you'll find some useful 'reading lists' to take to the library!
I suppose there's a risk that you might be duplicating school books, but at least it keeps you well away from the dreaded Magic Key and other reading schemes....