One of my primary Duck Hunting Mentors left his collection of HUnting, Fishing and just overall outdoors books to me when he passed away. He had a habit of underlining things, making notes in side bars and leaving Cards like birthday and Christmas Cards tucked in at appropriate points in the book. He also left smaller newspaper and magazine articles at pages which covered that subject. It's a wonderful way to have an enhanced view of his life and times. Yes, it reduces value by "defacing" the copy but to me it enhances the personal value. These books will be passed on to my Son with my added info .