Vol III 'A book is more usable and more marketable if it is well indexed. Five Star Publications, AZ, USA,1996 'All nonfiction books should have an index to enable readers to find information quickly and easily. Indexes are tools of accessibility. If they are poorly made and cannot do the job for which they are intended, they frustrate the readers. Simply put, a bad index diminishes a book.
Some books live or die by their indexes.
Indexing cannot be mechanized and its largely anonymous practitioners need much flair and intuition to accompany the automated approach. A good index can be much more than a guide to the contents of a book.