Different than a diary or a journal, the commonplace book focuses on material gathered from others. Its power for creativity lies in the opportunity it provides its maker to see the similarity and differences of what others have said about a given topic, to note the range and gaps. Commonplace books also serve as a writer’s personal pantry of quotations to add to their own creations.
from David Stone’s Inlandia Literary Journeys: Consider ‘commonplace book’ as alternative to a journal February 17, 2018
Read my whole column on commonplace books as it appeared in The Press Enterprise newspaper.
David Stone 
One of my college professors had the students do this with our class reading. I still have that notebook 40 years later. He commented on the entries. It was the most enjoyable assignment I had.