I assume it's natural that all coin collectors accumulate books relating to their collecting interest.   I have a collection of books. Sometimes my small library  seems huge to me, and when I can't find information I am looking for it seems barely adequate.  As with coins I have a hunt list of books I want.  Some references are long out of print; in one case a tatty copy of one book took me 2 years to find. Given that its publication date was 1808 2 years wasn't a surprising length of time.