The book of Ezra is about the nation of Israel's second exodus. The first exodus was such a big deal that there was an entire book devoted to it (aptly named Exodus), but this one doesn't get as much attention.
Israel has been in captivity for a good long while...about 70 years. Nearly the entire country, the part that wasn't slaughtered, was carried off to live in Babylon and in Ezra, Cyrus the king of the Persian empire is moved by God to rebuild the temple in Jerusalem. You can tell this is an act of God because proud conqueror-type guys don't usually decide to rebuild houses of worship in long-defeated countries far away. There's nothing in it for Cyrus except God's approval. Not only does he want the Israelites to leave and build the temple, he's going to finance the journey and encourage his citizens to give the Israelites gold and supplies.
Chapter 2 lists the people who leave Persia to go back to Judah, but it lists them by family not by individual names. Verse 62 has an interesting note about the descendants of Israel, because a bunch of families want to be registered as Israelites to go back and build the temple, but their bloodlines have been so muddied and the genealogical records so misplaced that no one can be certain that they count as Israelites. That's a sad state of affairs--after 70 years in captivity, God's people have gotten slightly mixed up about who's who. But nothing's a mystery to God, and it is said that the people with questionable family trees will be checked out with there is a priest ministering with the Urim and and Thummim to find out the truth. 42,000 Israelites in total go back to Judah and they all settle down in their cities.
The priests re-establish the burnt offerings and holy feasts of the past, and Levites are appointed to help with the temple work. The builders lay the foundation for the temple, and most everyone's so happy that they scream and shout for joy. But some of the old people in the congregation actually remember the first temple, and the image of how far they've fallen makes them cry. The noise of the tears and joy mingles together and is heard a long way off.
But though the foundation is laid, it's not long before some nasty bureaucracy gets in the way of the temple's rebuilding. For one thing, Cyrus dies and king Artaxerxes doesn't have such a high regard for Israel as his predecessor. He orders the building stopped so that the Israelites won't get any ideas about independence and revolt when their temple is complete. But no king lasts forever, and just as Cyrus' decree was revoked by Artaxerxes, Artaxerxes' decree is undone by king Darius. After Darius gives the go-ahead to finish the temple, it only takes about four years to complete it.
The titular Ezra doesn't appear until Chapter 7, where he goes up from Babylon and heads toward Jerusalem to help out in a few different ways. Ezra is a scribe, an intellectual person, but he also has practical abilities, and beyond these qualifications of talent, he loves the Lord : "For Ezra had prepared his heart to seek the law of the Lord and to do it, and to teach in Israel statutes and judgements" (7:10) Ezra finds his Israelite brethren in serious need of remembering God's law--plenty of the people have intermarried with non-Israelites, which is a serious no-no. Ezra is distraught and weeps before God, begging for mercy.
In present times, almost no one can grasp the severity of this issue. Marrying outside of your culture can be considered cool, and marrying outside of your faith is getting more and more common. In the Old Testament, marrying someone who doesn't love God is not a simple matter of being nontraditional, it's an inexcusable sin. Plenty of non-Jews converted (Rahab from Canaan comes to mind), but the foreign wives mentioned in Ezra have not converted. They still worship their gods, and the Israelite husbands thought this was okay until Ezra spoke up. The book of Ezra ends with a determination on the part of numerous men to divorce their foreign wives. Again, this sounds cruel to modern ears. How could these men abandon their wives? Well, they abandoned their God first, back when they chose to marry those wives. Horrible decisions lead to horrible consequences down the road. Fortunately, we now live in an era of mercy. God's mercy is available for those who ask for it, and He's not likely to ask you to divorce anybody, though you might be surprised at what He will ask.