Not only am I an author, I’m also a bookseller. I often think about things I can share with my followers while I’m working.
One of the things I notice is hot selling items.
Character Guides are huge in the children’s department. Kids are crazy about finding out all the details of their favorite characters. They also provide pictures and back story.
Usually a character guide consists of several pages devoted to the main characters from the series. A picture or pictures are provided, as well as details such as date-of-birth, birthplace, family tree, etc. Other characters may have one page with fewer details depending on their importance and presence in the series.
So, if you’re publishing a series of books, you should really consider creating a character guide to go along with it. Warriors The Ultimate Guide is a great example.