Walter Dragun's Town by Sheila Sancha is about Crafts and Trades of the Middle Ages. You could learn what business was like in the time of castles.
Cross-Sections CASTLE by Stephen Biesty. It tells you what it was like in a Castle under siege or a castle in peace time. I mainly like the pictures, because they look like you're really looking at the castle. In the book, there's a spy hiding in each picture, which you can find!
David McCaulay's Castle book tells you the story of a castle - what it's construction was like, what it was for, what tools they used to construct the castle, what weapons they had, and much more. David McCaulay has written several other books, such as Cathedral, Roman City, Pyramid, and Underground. All of his books tell you a story with great drawings. There is a video for his books too!
are two Eyewitness books that I like. One is about knights, knights' equipment,
and what knights actually did. Their book about castles has great pictures and
lots of infomation.
Other recommendations that I got by e-mail:
"I have a favorite book about castles that you might like to hear about. "Castles" by Philip Steele --Kingfisher Publishing, 1995. It has a lot of information about knights, sieges, jousts, chivalry and feasts.