The value of this book is when it is read with "The Basic Formulas of Fiction" by the same author. The meat of Foster-Harris' theory is found in "The Basic Formulas of Fiction", however, "Basic Patterns of Plot" complements the other text by discussing variations in plot patterns and provides a list of exemplary stories to illustrate his discussion.
This book does no harm. It is not a waste of time to read. But, it only becomes a strong piece of writing when read in conjunction with the above mentioned companion volume.