Zephaniah is another book proclaiming destruction, as most of the minor prophets' books are. Verse 2 of chapter 1 says "I will utterly consume all things from off the land, saith the Lord." The destruction will be coming because God's people the Israelites (specifically those that live in Jerusalem) have turned to idol worship again, and they think that the Lord has no power. They "say in their heart, The Lord will not do good, neither will he do evil" (1:12). Chapter 2 offers a solution by telling the people to "seek righteousness, seek meekness: it may be ye shall be hid in the day of the Lord's anger". And Jerusalem isn't the only place that will be eventually wrecked--the five Philistine cities, Moab, Ammon, Ethiopia, and Assyria are slated for demolition, too.
But after the badness, some good things will remain for God's people. 3:13 says, "The remnant of Israel shall not do iniquity, nor speak lies; neither shall a deceitful tongue be found in their mouth: for they shall feed and lie down, and none shall make them afraid." So the remaining Israelites will eventually be both godly and thoroughly protected from misfortune. Also, for all the fire and brimstone, Zephaniah contains one of the loveliest and most comforting verses in the Bible, in my opinion at least: "The Lord thy God in the midst of thee is mighty; he will save, he will rejoice over thee with joy; he will rest in his love, he will joy over thee with singing"(3:17). I sing when I'm really happy about something, and it makes me glad that God is the same way. :-)
The book of Haggai is 2 chapters long and deals with the prophet Haggai trying to exhort God's people to rebuild the temple in Jerusalem. The Babylonian captivity is over, but the Jewish people have just not put forth much effort to finish the house of God. Haggai encourages Zerubbabel the governor of Judah, and Joshua the high priest in their rebuilding efforts.