First Corinthians, or First Corinthians, was written by the Apostle Paul (who wrote about half of the New Testament). It is a letter, or epistle, to the church in the city of Corinth (the first of two that Paul wrote; see Second Corinthians for the second letter). It was written about the same time as Romans.
The book of first Corinthians is a practical letter of instruction revolving around life issues and addressing problems. As such, it is not a cohesive book with a unifying theme, but instead a series of teachings that were appropriate to the issues and struggles that faced the Christian church in Corinth.
A reoccurring theme in First Corinthians is the tension between the church and the world, that is godly living versus a worldly lifestyle. As such it’s a most appropriate and applicable book for our present age.