The Science of Harry Potter: How Magic Really Works
By Roger Highfield This book takes the fantasy and magic part of Harry Potter and explains the science and folklore/ mythology behind it.
The End of Harry Potter?
By David Langford This book was written before the release of the final book, Harry Potter and the Deathly Hallows. Its purpose was to explain some of the mysteries behind some of the stories.
Mapping the World of the Sorcerer's Apprentice: An Unauthorized Exploration of the Harry Potter Series
Edited By Mercedes Lackey This book contains essays written by fantasy and science fiction authors that discuss topics and issues implied in the series.
Fact, Fiction, and Folklore in Harry Potter's World: An Unofficial Guide
By George Beaham This book depicts the myth, legends, folklore, and literature behind the Harry Potter series. The beasts, wizards, and magic are all discussed and explained.