You know the issue. You enter a perfectly ordinary search term into Amazon - a term that seeks a quality answer to a logical question - and what do you get? Do you get a carefully built list of results that offers a strong answer to the question you arrived with? Or do you find the results a bafflingly hard-to-read collection of titles, only some of which look like books of real quality?
If you don't know what I mean, try it. Enter "crime thriller" or "suspense" or any other broadly thematic search term into Amazon's search bar. (I've mostly used examples from Amazon.co.uk in this piece, but the issue is the same on either side of the Atlantic.)