John Clements has a beginers one that has great basics for single sword, sword and shield ( round and heater types), longsword and others. I have it and have recomended it to many.
Unfortunatley the early period in which sword and shield was being used extensivley is really thin on actual period material. So these books are good fillers.
http://www.amazon.com/exec/obidos/ASIN/ ... 88-2155257
He heads up the ARMA organization so he knows what he is talking about. The ARMA site is LOADED with good research.
www.thearma.org
There is some good sword and buckler info out there, which is a highly underrated weapon combo. Once you figure it out, its very fast and very brutal. Great fun!
http://www.thearma.org/essays/SwordandBuckler.htm
Read and study everything you can about Liechtenauer- he's the Godfather of most subsequent masters-
http://www.thearma.org/essays/LeignitzerSandB.htm
A really good set of drills to go through are here- if you can incorporate these techniques into your fighting, you will be amazed how well they work:
http://www.thearma.org/essays/Leignitze ... tplays.htm
And of course the I.33 manual:
http://www.thearma.org/Manuals/i33/i33.htm
If you need help with I.33 there are 2 really good books out there to help:
http://www.revival.us/index.asp?PageAct ... &ProdID=98
http://www.revival.us/index.asp?PageAct ... ProdID=112
If you just want sword and shield only there is not much real period material in existance. If you want to incororate longsword - then there is TONS of material to glean through. Hope this helps.