Hi,
In Germany the first scientific book about Wikipedia has been published:
Frost, Ingo: Zivilgesellschaftliches Engagement in virtuellen
Gemeinschaften. Eine systemwissenschaftliche Analyse des
deutschsprachigen Wikipedia-Projektes. München: Herbert Utz Verlag,
2006. 152 S., € 29,00. ISBN 3-8316-0609-9
It's the diploma thesis of Ingo Frost, accesible at
http://www.cogsci.uos.de/~ifrost/
an english abstract is at
http://www-lehre.inf.uos.de/~ifrost/offiziell/engl_abstract.html
Wikimedia Germany has supported the printing.
More scientifc works of Wikipedia research can be found at
http://bibliography.wikimedia.de/
And it's getting more with Wikimania and WikiSym conferences in August.
According to his weblog Andrew Lih is writing a book about Wikipedia so
you will also get a book in English, but we were the first, afaik ;-)
Greetings,
Jakob