Roy,

A tip on scanning phone books (though I don't know if you made that scan): put a piece of dark paper behind the ad that you're scanning and it will eliminate a lot of the shadow that shows through the paper

Here's an example...I made the scan on the left, then stuck a piece of black paper behind the ad and scanned it again with the same settings. You can see there's still some shadows, but they aren't as prominent

(when I previewed the post, I was surprised at the color difference...I really didn't change any settings!)