William Guthrie, a Scottish minister, published this, his only book in 1658. Some men only need to write one book in their entire lifetime to say something truly profound-Guthrie was one of them. How do we know whether we have a special saving interest in Jesus Christ and how can we obtain it if we find that we don't? These are the two questions William Guthrie concerns himself with in the book, "The Christian's Great Interest." This book is a classic work on assurance of salvation and evangelism by a seventeenth century Presbyterian author. To Guthrie, how we answer the question about our salvation is of the greatest interest to all people. It is "not a vain thing because it is your life," and it is "the one thing needful." Our salvation is discernable if we examine our case from the scripture. "To the law and to the testimony if they speak not according to his word, it is because there is no truth in them." The bible commands us "examine yourselves, whether ye be in the faith; prove your own self," "give diligence to make your calling and election sure." An exceptional book, "The Christian's Great Interest" was recommended by noted Christian author John Owens.