False.This man speaks the truth.
Many enchantments have sweet spots where they are more common.
As aside I don't have issues with using books. I just keep my unwanted ones for use in Thaumcraft for there aspects.
Quit posting misleading statements.
Open Excel document. Go to "Pivot Table" tab, up top change to "Book".
Fortune III the sweet spot is LV 30. Pretty much all of the top-tier GOOD stuff on Books is only available at LV30 (other than Unbreaking, where you can do LV20). Silk Touch I is the exception, but if I have a decent spawn farm, I just do LV30 anyway since I'm enchanting 100 books and I'll get other good stuff.