One of the best books written on the topic of takfir with an introduction of Mawlana Yusuf Binnori:

http://www.serveislam.com/webapps/si...aDetailID=9167

The original book in Arabic can be downloaded here with tasdiqat in the end: http://www.4shared.com/get/0HZPCD8v/...B81289B9.dc211