Marshall Stillman was an amateur boxer and instructor.  The 1919 book, Boxing and Self Defense Taught by the Marshall Stillman Principle, published by the Marshall Stillman Association, begins this way:

"MARSHALL STILLMAN has been a student of boxing for more than thirty years. He was a pupil and intimate friend of Professor Mike Donovan who retired undefeated middleweight champion of the world and who taught boxing at the New York Athletic Club for thirty years.  

Professor Mike Donovan thought so much of Marshall Stillman and the "Shorthand" or "Sub-Conscious" Method of teaching Boxing that he heartily endorsed both, and posed for the illustrations in this book. This is Donovan's system of boxing taught by Marshall Stillman's principle of instruction.

Marshall Stillman's interest in boxing and self-defense for the last ten years has been devoted largely to the development of this simplified system of instruction. Anybody, young or old, can learn the rudiments of boxing and how to guard against attack from this course. Boys of 12 and 15, have learned; men of 40 and 60 have learned, and what is more, they have benefited physically as a result." 

This is one of a series of small softback books, 8" by 5", published between 1920 and 1922, by the Marshall Stillman Association of New York.  This one is titled and subtitled, "Shadow Boxing : How to Train Advice on Living Rules of the Ring".  It is Book Four of a series of books - I'm not sure of the size and composition of the entire set.  It is in GOOD OR BETTER CONDITION.  There are two small stain dots (maybe drops of a liquid?) seen on the front cover.  There are a few tiny tears on the front cover - right fore edge - and a few tiny tears at this location after the cover.  Otherwise 48 clean and solidly staple bond pages with no marks, many B&W photos."

SM1