I had to read it for grad school and it was not my favorite but there is so little written on how to determine the subject of a resource for cataloging purposes that it still holds value. Written in the late 80s, this book is quite dated in its description of specific classification schema but there is a fairly good section extrapolating in the nature of thought. Of most use is the chapter Summarization in Practice which gives many detailed examples of how complex the breakdown of subject and aboutness truly is. But subject analysis is only truly learned by doing, reading about it in theory can feel kinda useless.