Best consulting books - top 20

A list of the most recommended books on consulting, based on a synthesis of 20 of the supposedly most valuable lists of best consulting books available on the internet: https://www.blog.consultants500.com/consulting/top-20-best-consulting-books-recommended-times/ . 

The above list is US-oriented.  For a British perspective, Calvert Markham's book 'The Art of Consultancy' is now in its 7th edition.