Ghosts are a good topic for the series, The Unexplained, because many people have differing opinions on whether or not they exist.  This book presents both points of view with supporting explanations.  Although there is no solid proof either way, the reader is left to form their own beliefs.  There are stories of ghosts and color photos along with a glossary, index, and sources for more information.  This 24-page book provides a balanced beginning introduction to ghosts.