A better example might be book publishers; do we really need any C books beyond K&R, or at most, K&R plus van der Linden? Maybe not, but there's dozens of them

A better example might be book publishers; do we really need any C books beyond K&R, or at most, K&R plus van der Linden? Maybe not, but there's dozens of them anyway. Different books on the same topic might be selected based on anything from number of pages to familiarity with the publisher and/or author to typesetting to cover graphics to thoroughness of the index to reviews on Amazon.com to addressing niche needs (or perceived needs) of a particular target audience to ... Even today, with lots of programmers wishing C would just die forever, I suspect a publisher could put out a new book on C and make it profitable if they found the right criteria.