R. A. Torrey was an American evangelist, a Bible scholar, and successor to D. L. Moody. A graduate of Yale, he was ordained to the ministry in 1878.

In the opening chapter, Torrey describes the purpose of his book. "We begin herewith a series of studies of the person and work of the Holy Spirit. We shall begin this series by considering what the Bible has to say about the Holy Spirit as a person. It is impossible to rightly understand the work of the Holy Spirit, or to get into right relation with the Holy Spirit Himself and thus know His blessed work in our own souls, without first coming to know the Holy Spirit as a person. One of the most fruitful sources of error and misconception, of unwholesome enthusiasm and false fire and fanaticism, in the treatment of this whole subject, is from trying to know the work of the Holy Spirit before we first come to know the Holy Spirit Himself."

This book is a must-read for those who want an in depth further understanding of the Holy Spirit.