Notes, highlighting, or underlining from a past reader that is found in a library book or a used textbook and helps the current reader. Like the helpful notes Harry Potter finds in his Potions textbook in the sixth book/movie.
"Man, taking notes last night took forever!"

"Not for me. I got some half blood prints up in this copy of Grapes of Wrath. Everything I needed was already highlighted."
by Watershipstem of a Down March 11, 2012
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