David M. recommends Castles: Their History and Evolution in Medieval Britain by Marc Morris

This book is what makes history writing interesting when done well. Morris tells the reader about what is known of the personalities of those individuals who had them built as residences. He also discusses the changes in their architectural styles over time, along with weapons used in defending them.
Publisher's description:
This book is what makes history writing interesting when done well. Morris tells the reader about what is known of the personalities of those individuals who had them built as residences. He also discusses the changes in their architectural styles over time, along with weapons used in defending them.