Here is the movie we watched today.  I got it from the library.
https://opac.cadl.org/record=b1544334~S15

This is a book I found while I was looking for that movie.  I found the parts I've read so far absolutely fascinating and a few students who had a chance to look at it seemed interested in reading more.  It has lots of footnotes and pictures if you want to do more research and I'll bring it next week in case we have time for anyone to look at it some more.  It can also be found at the library
https://opac.cadl.org/record=b1945117~S15

The book we didn't get to today.  It has pictures and explanations of several different kids of castles throughout history. 
You can get it at the CADL.
https://opac.cadl.org/record=b1885261~S15