Their Medieval list just came out in May and contains a Mongol page. Currently if you look at some of their pages you might be scared of some of the prices. They are in pounds and someone typed in 3 instead of some of the pound symbols. They are going to fix it. They currently convert the pounds into dollars at 1.8 X pounds to cover transatlantic shipping costs.
Some books are cheaper though if they have American or Canadian editions.
They sell new and expensive asian books on many subjects. Tattershall Trained Band Jeff and Caroline's 17th Cent. Sir Marmaduke Rawdon's Regiment Coll. The Siege Group Syke's Sutlery The Society for Creative Anachronism Inc. For when you want that book, or trying to find information on that particular item, locations, attendance times, etc.