Here's what his thoughts on reading the bible and prayer. This was quite inspiring and I am sharing this with you all. God bless you.
Sundar seldom talked publicly of his devotional life, though his addresses were the product of much meditation and prayer. Now and again he opened his heart to his friends however.
"Rising Early, I begin by reading a chapter of the bible. I make a mental note of the verses which seem suggestive," he told his friends who asked about his methods of meditation. "Then, when I have quietly read the whole chapter, I return to each of these verses and meditate on them, one at a time. After I have exhausted all that God can say to me through those verses at that time I spend a quarter of an hour 'collecting myself' for prayer."
"I have no special posture for prayer. I may sit, or kneel, or stand. I use no words. I think only of those things that I have been reading, of the things I have been doing or intend to do, of the people I know, of myself and of Jesus- such thought is prayer. And in such prayer, God speaks, not man."
Finding a book on him is quite difficult. Here are some links online which I found
A Brief Biography : http://sadhusundarsingh.homestead.com/files/introduction.html
Wiki : http://en.wikipedia.org/wiki/Sadhu_Sundar_Singh


