Here are some must-read books on Wright, many with a focus on his Japan work:

The Architecture of Frank Lloyd Wright
by Neil Levine. Princeton, New Jersey: Princeton University Press, 1996.

The Architecture of Frank Lloyd Wright: A Complete Catalog
by William Allin Storrer. Third Edition. Chicago: The University of Chicago Press, 2002.

Frank Lloyd Wright by Robert McCarter. London: Reaktion Books Ltd.,2006.

Frank Lloyd Wright and the Art of Japan: The Architect's Other Passion
by Julia Meech. New York: Harry N. Abrahms, Inc., 2001.

Frank Lloyd Wright and Japan: The Role of Traditional Japanese Art and
Architecture in the Work of Frank Lloyd Wright

by Kevin Nute. New York: Routledge, 2000.

Frank Lloyd Wright's Fifty Views of Japan: The 1905 Photo Album
by Melanie Birk, Ed. San Francisco: Pomegranate Artbooks, 1996.

Frank Lloyd Wright's Imperial Hotel
by Cary James. New York: Dover Publications, Inc., 1988.

Frank Lloyd Wright: The Interactive Portfolio
by Margo Stipe. Philadelphia: Running Press, 2004.

Measured Drawings of Wright's Japanese Work
by Masami Tanigawa.Tokyo: Shokokusha Publishing Co., Ltd., 1995.