I have a habit of underlining my favourite passages in whatever book I'm reading. My opinion is that underlining in books just adds to the value, and I especially love to buy a book used and find that someone else has already done the same...or even made notes in the margin. Some kind of literary connection of a sort.
What do you guys think?
What do you guys think?

Personally, I don't like books that have been underlined before me. In college, it was idiots who underlined everything inconsequential. In regular books, people don't realize what is really important in the book like I do.