GIJOE & matchan will release a book for XOOPS customizing on the end of April.
You can see the Japanese information from the publisher's site.
http://book.mycom.co.jp/book/4-8399-1779-5/4-8399-1779-5.shtml
This is a simple translation
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"Customizing XOOPS" -designing and hacking with ease-
Author: GIJOE & matchan
Price: 3,150yen
Size: almost B5
Pages: 520
ISBN4-8399-1779-5
Releasing date: 22 April 2005 (Perhaps...)
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Do you know matchan?
He is one of the coolest theme designer.
If you don't know matchan, go to http://www.oceannet.jp/ right now