Comment by ortusdux

I once took a critical thinking course and bought the textbook 2nd hand from the college bookstore. A week or two in, I noticed half of a sentence written in the margin. As the professor started teaching the topic from that page, he rhetorically asked a question, did not get an answer, and then answered himself with the sentence from the book. I filliped ahead and found that the entire book was annotated with all of his answers, anecdotes, and various other helpful notes. There was even a table that accurately listed his wardrobe choices! The notes were in several different handwritings, and the book had been resold over a dozen times, so that professor must have been teaching the same class the exact same way for a decade or more. I quickly became a star pupil as I always had an answer ready. I added a few notes along the way and then sold it back to the bookstore at the end of the year. I really wanted to keep it for posterity, but It just seemed wrong to take it out of circulation.