I cannot conjure up the effrontery it would take to scribble marginal notes in a borrowed book.
I remember borrowing a copy of George Santayana’s Life of Reason (the one-volume edition) from a local library and reading the inane commentary of a previous reader. It actually turned me off reading the book.
I made up for this by buying the book in its first, multi-volume editions. Alas, I have only read two of its five parts, and own a mere three of them. This is not the origin of my entry into the ranks of the bibliobibuli, or of book collectors, but it may have been a turning point of sorts.
So I may owe something (what, you decide) to one particular Pacific Northwest graphomaniac.