Who was the author? As with 1 Corinthians, the Holy Spirit inspired the Apostle Paul to write the book we know as 2 Corinthians.
What is the book? The book is an epistle (or "letter") to not only the believers in Corinth but, according to 2 Corinthians 1:1, also to all the other Christians in Achaia (the Roman province at the time that included all of Greece south of Macedonia).
Where was it written? The letter is thought to have been written from Macedonia (see 2 Corinthians 2:13; 7:5).
When was it written? The letter we know as 2 Corinthians is thought to have been written before winter began, just months after 1 Corinthians, which was likely written in the spring of A.D. 55.
Why? The usual theory is that after Timothy delivered 1 Corinthians to its recipients and worked among them for a while, Timothy brought back a bad report to Paul, who himself made a "painful" visit to Corinth and wrote a "severe" letter. Titus is thought to have bore that letter and brought better news back to Paul who then wrote the letter we know as 2 Corinthians, which addresses some of the same challenges facing the people that were addressed in 1 Corinthians.
How? In one analysis, Paul is seen in 2 Corinthians as addressing his past, present, and future actions and ministry. In another analysis, Paul is seen as using the letter to address his upcoming third visit to Corinth, explaining the reason his itinerary changed earlier, encouraging the people to complete their collection, and vindicating his apostolic authority.
For further reading on the book of 2 Corinthians:
- Kretzmann, Paul E. Popular Commentary of the Bible: The New Testament, Volume II, The Epistles of the Apostle Paul, The Epistle to the Hebrews and the Catholic Epistles, the Book of Revelation. St. Louis: Concordia Publishing House, 1922. (This often helpful volume has 56 pages on 2 Corinthians.)
- Lenski, R. C. H. The Interpretation of St. Paul's First and Second Epistle to the Corinthians. Columbus, Ohio: Wartburg Press, 1946. (Although reprinted in 1947, this commentary was first published in 1937 and so is out of date as far as scholarship goes, but his interpretations are nevertheless generally reliable and quite accessible to most readers. The volume has some 551 pages on 2 Corinthians.)