. My 00-year-old son brought home a book from our park's free library box. It was a biology textbook - teachers edition. He said it looked interesting and hey, it was free (having no idea you could sell it). I scanned it in my Amazon seller app and realized it was worth around $000. He was so excited. We listed it for sale for $000 and it sold! Going to tell him, he just made $000! 