> I'm not a religious person but for me paper books are sacred. I would never mark in a book(…) You might be surprised by how many religious people profusely a

> I'm not a religious person but for me paper books are sacred. I would never mark in a book(…) You might be surprised by how many religious people profusely annotate their sacred texts. :) But I see your point: to keep the book undefiled so it can have a long useful life and perhaps even be passed down generations. However the point is utilitarian, not sentimental: the purpose of books is to expand the mind of the reader, and in the age of cheap printing the book can be molded to its reader. When you go back and read a book, you can get a better glimpse of what you were thinking the previous times you read a section, and reflect on whether that position confirmed over time, got invalidated or perhaps became a bit more nuanced.