as far as I know there isn't documentation for kirikiri engine in english, the Japanese documentation can be found here :
http://devdoc.kikyou.info/tvp/docs/kr2doc/contents/
http://devdoc.kikyou.info/tvp/docs/kag3doc/contents/
http://devdoc.kikyou.info/tvp/docs/tjs2doc/contents/
fortunately there is someone begin translating the document, you can contact him here : http://kirikiri-i18n.sourceforge.jp/