C. K. Barrett 
Second Epistle to the Corinthians [PDF ebook] 

’Second Corinthans is one of the most difficult writings in the New Testament to interpret. Yet, this commentary, which follows Barrett”s works on Romans and I Corinthians in the same series, is superb in every respect. The author”s command of the Greek language, his skillful use of the Old Testament and background writings, and his sensitive handling of complex exegetical problems provide a panorama of a mature scholar”s work which is at times almost breathtaking. Moreover, the restrained use of Greek and technical terms makes this commentary as useful for the layman or pastor as it is for the scholar.’
-Review and Expositor