Wikipedia
Ezra–Nehemiah is the original combined version of the biblical books of Ezra and Nehemiah—the two were originally one, but were divided by Christians in the 3rd century CE and in Jewish circles in the 15th century. Covering the period from the fall of Babylon in 539 BCE to the second half of the 5th century BCE, it tells of the successive missions to Jerusalem of Zerubbabel, Ezra, and Nehemiah, and their efforts to restore the worship of the God of Israel and to create a purified Jewish community. The narrative is highly schematic, each stage of the restoration following the same pattern: God "stirs up" the Persian king, the king commissions a Jewish leader to undertake a task, the leader overcomes opposition and succeeds, and success is marked by a great assembly.
In the 19th century and for much of the 20th, it was believed that Chronicles and Ezra–Nehemiah came from the same author or circle of authors (similar to the traditional view which held Ezra to be the author of all three), but the usual view among modern scholars is that the differences between Chronicles and Ezra–Nehemiah are greater than the similarities, and that Ezra–Nehemiah itself had a long history of composition from many sources, stretching from the early 4th century down to the Hellenistic period.