Paul's second letter to the Corinthians is probably the least known of all his letters. It has sometimes been called "Paul's unknown letter," and I do not know why that is. First Corinthians is very well known among his writings, but many people feel that Second Corinthians is heavy reading. It is too bad that we are so unfamiliar with it, because it represents the most personal, autobiographical letter from the apostle's pen.
In First Corinthians the focus is on the church at Corinth. But in Second Corinthians we are looking at Paul; he is the one in focus as he lays himself open and reveals himself to the church. This, therefore, is a very personal letter from the heart of this mighty apostle. Here we see him more clearly, perhaps, than anywhere else in Scripture.