First and second Chronicles in the Old Testament was originally one book, but since the time of the Greek Septuagint, the book was translated and appeared as two separate books, which continues today. Around 540-35B.C., the Medes and Persians defeated Babylon and became the major power in the Middle East and Asia.
Shortly after coming to power, Cyrus, king of Persia, invited the Jews to return to their homelands after more than fifty years in captivity. When the returning exiles arrived they were not granted the status of an independent nation with a king of their own, for they were still under the authority of Persia.
For those Jews returning from exile, temple service and obedience to the law were stressed as the source of divine blessing. This emphasis succeeded in curing Israel of one sin that had plagued them since their deliverance from Egypt, that being idolatry. Over time however, idolatry of a different kind replaced the pagan idolatry. The "Law" itself became so important to some of the Jews that by the time of the Savior's mortal ministry they worshiped the "law" but rejected the Savior.
The author of both Chronicles is not known, but we do know that the books were completed in approximately 538B.C. after the Jews returned. The books are in part, a post-exile sequel to the histories in the books of Samuel and Kings, and the books of Ezra and Nehemiah which follow Kings, are the historical continuation of the books of Chronicles.
The chief focus of Chronicles was to help the returning exiles remember their relationship with the Lord and with the previous united nation of Israel. Almost half of the material in Chronicles is taken from the previous books of Samuel and Kings, but the author only incorporated material he felt helped the people see themselves as God's chosen people. The author emphasized the glory of the temple Solomon built and the importance of temple worship, along with the history of the kings of Judah.