The Book of Ezra

Ezra was a priest and scribe, a man learned in matters of the Lord's commandments and his statutes for Israel (Ezr 7:6a, 11). Ezra had set his heart on studying the
Mosaic Laws, to follow them and to teach these Laws in Israel (Ezr 7:10). According to Jewish tradition, he also compiled the Chronicles and perhaps even the Psalms.
He moved from Babylonia to Jerusalem, which was under Persian rule 
(Ezr 7:6 (1 in some translations), 8–9). Ezra also collaborated with Nehemiah 
(Neh 8:9, 12:26), see The Book of Nehemiah.

The Book of Ezra has the following content:

Chapters 1–3: Ezra describes what has happened before his own time: how the
Jews returned to their homeland by a decree of Cyrus, the first king of Persia.

Chapter 4: How the temple building came off because of the resistance from
the people who lived in the land and were adversaries to the Jews.
(It also describes the resistance to rebuilding the walls around Jerusalem,
which later occurred during the reign of Artaxerxes I, the fifth king of Persia.)

Chapter 5–6: How the temple construction was able to proceed by obtaining the permission of Darius I, the third king of Persia, and with the support of Haggai and Zechariah.

Chapter 7–8: How Ezra strengthened the people's temple service when he arrived.

Chapter 9-10: How Ezra strengthened obedience to the Law (see also Neh 8). 

We have the following chronology for Ezra, Nehemiah, and Esther:

• 537 BC: The decree of Cyrus, the first king of Persia, to rebuild the temple
  (Ezr 1:1–4, Isaiah 44:28, 45:1, 4), see The Book of Habakkuk.
• 537 BC: Zerubbabel's expedition to Jerusalem (Ezr 2:2).
• 536 BC: The foundation of the temple was laid (Ezr 3:7–11).
• 535 BC: The temple work stopped (Ezr 4:4–5, 24).
• 520 BC: The ministry of the prophet Haggai began, see 
  The Book of Haggai and prophet Zechariah, see The Book of Zechariah.
  They prophesied that they would continue with the rebuilding of the temple. Zerubbabel, Jeshua, and the Jews obeyed and continued with the rebuilding. (Ezr 5:1–2, 14). See also the picture in The Book of Ezekiel.
• 516 BC: The temple was completed after being given permission to proceed by Darius I, the third king of Persia, father to Ahasuerus 
  (known as Xerxes I). (Ezr 6:1–15).
• 486 BC: The reign begins of Ahasuerus (known as Xerxes I), 
  the fourth king of Persia.
• 479/478: Esther is crowned queen, married to Ahasuerus, 
  see The Book of Esther.
• 465 BC: The reign of Artaxerxes I begins, the fifth king of Persia 
  (son to Ahasuerus). The rebuilding of the walls is stopped during his reign (Ezr 4:13, 21–23).
• 458 BC: Ezra moves to Jerusalem with several other Jews during the reign of Artaxerxes I (Ezr 7:1, 8–9, 13, 28, 8:1–13, 18–20).
• 445 BC: Nehemiah arrives to Jerusalem (Neh 2:11).
• 445 BC: The walls of Jerusalem are completed after 52 days (Neh 6:15).
• 433 BC: Nehemiah returns to Persia but will later return to Jerusalem.

The Persia king Artaxerxes I stopped the rebuilding of the walls of Jerusalem (Ezr 4:13, 21–23). This probably occurred at the beginning of his reign. Later he instead favored
Jerusalem and its temple by sending Ezra (Ezr 7:11–28) and Nehemiah

(Neh 2:1–9) to Jerusalem. 

Ezra and those who came with him from the Babylonian captivity, offered Burnt Offerings to God when they returned to their homeland
(Ezr 8:35).

Afterwards the officials came to Ezra and said that the people of Israel and the priests and the Levites hadn't separated themselves from the peoples of the lands with their abominations. For they had taken some of their daughters as wives for themselves and for their sons. And in this faithlessness the hand of the officials and chief men had been foremost. (Ezr 9:1–2). See for example Samson.

This was against the Mosaic Laws (Deu (5 Mos) 7:3, Mal 2:11). The reason was that intermarriage would turn them away from the Lord and they would start serving other gods. If they did, the Lord's wrath would come upon them.
(Deu (5 Mos) 7:4). This was also a reason why they ended up in exile, something that Ezra understood (Eze 9:3, 7, 10–14).

Ezra had great influence on the people of Israel, but it was also a work of God 
(Ezr 10:1). "For you (God) will not delight in sacrifice, or I would give it; you will not be pleased with a burnt offering. The sacrifices of God are a broken spirit; a broken and contrite heart, O God, you will not despise." (Psalm 51:16–17 (18–19 in some translations)). Ezra was advised to make a covenant with God to send away all these wives and their children, to do it according to the Law, and that it was his job to do it (Ezr 10:3–4). 

The Jews probably would have lost their ethnicity and gone astray as a nation if they hadn't dealt with it. King Solomon, who was the wisest man in the world and loved by God, was led to sin by foreign women. His wisdom didn't protect him from it.
(Neh 13:26). God had a plan for Israel, Messiah would come from them, and therefore it had to be done, even if it wasn't easy for the people. 

Ezra gathered the people and told them that they had been unfaithful in marrying foreign women. They should separate from the peoples around them and
from their foreign wives. The whole assembly responded that he was right,
and that they must do as he said. (Ezr 10:10–12). It took three months to find out who of the people this affected (Ezr 10:16b–44). 

In the New Covenant that we live by, it's not an option to divorce a person just because that person is an unbeliever (1 Cor 7:12–16), see the 7th commandment in The Ten Commandments, and Jesus and the Law. 

See also The Old Testament of the Bible.