Buying Japanese textbooks[]
Japanese textbooks are sold in many of the large book shops in Tsukuba. The best place to find textbooks in Tsukuba is probably Maruzen at the University of Tsukuba campus.
If you can make the trip to Tokyo, Bonjinsha is THE place to buy Japanese textbooks. Other options include Kinokuniya in Shinjuku and Tower Records in Shibuya. There are many other book shops in Tokyo that stock Japanese texts.
If you already know what book you want, you can probably find it at Amazon.co.jp for the best price.
Borrowing Japanese textbooks[]