How do you feel about illustrations in your books? Graphs? Photos? Sketches?
If I am reading a book with a lot of characters, I appreciate a graph to help me to keep track of how everyone is connected to everyone else. I am thinking of books like One Hundred Year of Solitude and The Girl with the Dragon Tattoo as examples. I also appreciate photos and sketches if they help to illustrate part of a character's personality or illustrate their experiences. For example, books like The Curious Incident of Dog in the Night Time or Three Cups of Tea.