Over time, those books will scratch your burned discs. My Van Morrison Astral Weeks(amazing album) was torn to hell after 6 monthes. I never once dropped it. I also never leave CD's laying around.

I have two 200 disc books in my car with the soft backs(caselogic). It never seems to happen to regular cd's, but then again, CDR's are much more sensitive to smudges than regular CD's, also.