A Book Can Only Show You So Much

I'm a little bit annoyed that in every lecture I attend or in any book I read where they have cause to mention the triconsonantal roots of Arabic and similar languages, I am always presented with the example of k-t-b, book, (or libro the first time I learned about it). One text I have makes brief mention of a second root x-l-f, Caliph. It's barely used to illustrate anything, but at least they are trying.