http://www.amazon.com/Stepping-through-time-Archaeological-prehistoric/dp/9080104469
and
http://www.amazon.com/Craft-Industry-Everyday-Life-Anglo-Scandinavian/dp/1902771362/ref=pd_sim_b_2
are the other two (along with the Museum of London book "Shoes and Pattens") that are the must haves for medieval shoemaking. I noticed that "Stepping Through Time" has gone up a lot. Hopefully, you can find it for less.
Jon