The writer Giani Pritam Singh ji Mastana studied in a Missionary college and was a firm missionary. He was strictly against Sant mahapursh especially against Nanaksar. But in this book he explains how he got surrendered himself to Sant Isher Singh ji Kalerawale. Every time he would visit nanaksar to argue with Sant ji but his missionary logical arguments would vanish without Sant ji even utterring a word to him. It was just the way Sant ji used to look at him and he used to feel ashamed and guilty. And all this would happen without any conversation. The book answers all the questions that missionaries put against sikhi and sants.
http://jsks.biz/ishwar-darshan-giani-pritam-singh-ji-mastana
A must read. A very very beautiful book, full of love.
Unfortunately, the book is not available in pdf form to download online. Please do buy.