Amos 1: the Lord is against nations around Israel/Judah.

Amos was a sheepherd in Takoa, Judah. He received a message from the Lord concerning Israel when Israel was doing fine economically in times of Jeroboam II. Reading the Old Testament, we see that the Lord loved Israel despite its idolatry.
We read:

2 The Message:
God roars from Zion,
    shouts from Jerusalem!
The thunderclap voice withers the pastures tended by shepherds,
    shrivels Mount Carmel’s proud peak.

The temple is in Jerusalem, Judah and the Lord shouts from there. His voice can be heard in distant places such as Mount Carmel in Israel.
The Lord is against Damascus, Gaza, Tyre, Edom and Ammon. They mistreated the people of the Lord. For instance Gaza turned Israelites as slaves and sold them to Edom:

6-8 God’s Message:
“Because of the three great sins of Gaza
    —make that four—I’m not putting up with her any longer.
She deported whole towns
    and then sold the people to Edom.
For that, I’m burning down the walls of Gaza,
    burning up all her forts.
    (...)

One application of this text is that the Lord knows I belong to his people. Although I may be mistreated by others (because I belong to Him), I believe that the Lord is taking care of me. Eventually, He will deal with those that mistreated me.    

Joel 3: Judgement day

The book o Joel finishes saying:

1-3 “In those days, yes, at that very time
    when I put life back together again for Judah and Jerusalem,
I’ll assemble all the godless nations.
    I’ll lead them down into Judgment Valley
And put them all on trial, and judge them one and all
    because of their treatment of my own people Israel.
They scattered my people all over the pagan world
    and grabbed my land for themselves.
They threw dice for my people
    and used them for barter.
They would trade a boy for a whore,
    sell a girl for a bottle of wine when they wanted a drink.

Jerusalem is not alive as in older days. The Lord will renew Jerusalem in the last days. The Lord will assemble all the godless nations against Israel (are we in the last days?), but the Lord will defend His people:

15-17
“The sky turns black,
    sun and moon go dark, stars burn out.
God roars from Zion, shouts from Jerusalem.
    Earth and sky quake in terror.
But God is a safe hiding place,
    a granite safe house for the children of Israel.
Then you’ll know for sure
    that I’m your God,
Living in Zion,
    my sacred mountain.
Jerusalem will be a sacred city,
    posted: ‘no trespassing.’
Milk Rivering out of the Hills

It is difficult to understand with our heart that "God is a safe hiding place", but it will become very clear in the last days. Besides, the Lord is gracious:


18-21
(...) Meanwhile, Judah will be filled with people,
    Jerusalem inhabited forever.
The sins I haven’t already forgiven, I’ll forgive.”
    God has moved into Zion for good.
    

Joel 2: Repent before Judgement Day!

Joel 2 calls Israel to repent before Judgement Day. The Lord is preparing an army of locusts that will devour everything:

3 Before it arrives, the country is like the Garden of Eden.
    When it leaves, it is Death Valley.
    Nothing escapes unscathed.

11 God’s Judgment Day — great and terrible.
    Who can possibly survive this?

The Lord calls Israel to repentance before Judgement Day:

13-14
Change your life, not just your clothes.
    Come back to God, your God.
And here’s why: God is kind and merciful.
    He takes a deep breath, puts up with a lot,
This most patient God, extravagant in love,
    always ready to cancel catastrophe.
Who knows? Maybe he’ll do it now,
    maybe he’ll turn around and show pity.
Maybe, when all’s said and done,
    there’ll be blessings full and robust for your God!

The Lord will not only save his people from the locust but He will also pour His Spirit on his people:

25-27
“I’ll make up for the years of the locust,
    the great locust devastation—
Locusts savage, locusts deadly,
    fierce locusts, locusts of doom,
That great locust invasion
    I sent your way.
You’ll eat your fill of good food.
    You’ll be full of praises to your God,
The God who has set you back on your heels in wonder.
    Never again will my people be despised.
You’ll know without question
    that I’m in the thick of life with Israel,
That I’m your God, yes, your God,
    the one and only real God.
Never again will my people be despised.

28-32 “And that’s just the beginning: After that—
“I will pour out my Spirit
    on every kind of people:
Your sons will prophesy,
    also your daughters.
Your old men will dream,
    your young men will see visions.
I’ll even pour out my Spirit on the servants,
    men and women both.
I’ll set wonders in the sky above
    and signs on the earth below:
Blood and fire and billowing smoke,
    the sun turning black and the moon blood-red,
Before the Judgment Day of God,
    the Day tremendous and awesome.
Whoever calls, ‘Help, God!’
    gets help.
On Mount Zion and in Jerusalem
    there will be a great rescue—just as God said.
Included in the survivors
    are those that God calls.”

It is very interesting that Joel 2:28-32 is referenced in Acts 2:17-21. It is also interesting that the Lord will pour His Spirit before Judgement Day, in the last days; so we are living in the last days before Judgement Day.

Joel 1: We live in chaos.

Due to the consequences of sin, we live in a chaos, in a world that doesn't properly support life.
The locusts eat our food:

4
What the chewing locust left,
    the gobbling locust ate;
What the gobbling locust left,
    the munching locust ate;
What the munching locust left,
    the chomping locust ate.

The invader, our enemy, has eliminated the wine:

5-7
Sober up, you drunks!
    Get in touch with reality—and weep!
Your supply of booze is cut off.
    You’re on the wagon, like it or not.
My country’s being invaded
    by an army invincible, past numbering,
Teeth like those of a lion,
    fangs like those of a tiger.
It has ruined my vineyards,
    stripped my orchards,
And clear-cut the country.
    The landscape’s a moonscape.

There is no food in the sanctuary of the Lord:

8-10
Weep like a young virgin dressed in black,
    mourning the loss of her fiancé.
Without grain and grapes,
    worship has been brought to a standstill
    in the Sanctuary of God.
The priests are at a loss.
    God’s ministers don’t know what to do.
The fields are sterile.
    The very ground grieves.
The wheat fields are lifeless,
    vineyards dried up, olive oil gone.

God's judgment day has come:
    
15-18
What a day! Doomsday!
    God’s Judgment Day has come.
The Strong God has arrived.
    This is serious business!
Food is just a memory at our tables,
    as are joy and singing from God’s Sanctuary.
The seeds in the field are dead,
    barns deserted,
Grain silos abandoned.
    Who needs them? The crops have failed!
The farm animals groan—oh, how they groan!
    The cattle mill around.
There’s nothing for them to eat.
    Not even the sheep find anything.    

Hosea 14: The Lord heals the apostasy

The Lord is good, we are not. He wants Israel despite her apostasy. He calls Israel to repent, He teaches Israel what to say when repented.

1-3 O Israel, come back! Return to your God!
    You’re down but you’re not out.
Prepare your confession
    and come back to God.
Pray to him, “Take away our sin,
    accept our confession.
Receive as restitution
    our repentant prayers.
Assyria won’t save us;
    horses won’t get us where we want to go.
We’ll never again say ‘our god’
    to something we’ve made or made up.
You’re our last hope. Is it not true
    that in you the orphan finds mercy?”

The Lord is the One who heals, apostasy included:    
    
4-8
“I will heal their waywardness.
    I will love them lavishly. My anger is played out.
I will make a fresh start with Israel.
    He’ll burst into bloom like a crocus in the spring. (...)


What will be the response of Israel - the One who heals? Will Israel turn to the Lord? The following verses appeals Israel to choose to live well. The Father wants us to live by his side, and have a meaningful life.

9
If you want to live well,
    make sure you understand all of this.
If you know what’s good for you,
    you’ll learn this inside and out.
God’s paths get you where you want to go.
    Right-living people walk them easily;
    wrong-living people are always tripping and stumbling.

Hosea 13: life or death to Ephraim?

Most churches nowadays invite others to "accept Jesus" as his saviour. Hosea 13 goes in a different way to Ephraim. The Lord declares that He is the Lord of Ephraim, despite Ephraim sins of idolatry:

4-6
“I’m still your God,
    the God who saved you out of Egypt.
I’m the only real God you’ve ever known.
    I’m the one and only God who delivers.
I took care of you during the wilderness hard times,
    those years when you had nothing.
I took care of you, took care of all your needs,
    gave you everything you needed.
You were spoiled. You thought you didn’t need me.
    You forgot me.

It is very likely that a preacher would say something like to Ephraim: "as you worshiped false gods and made terrible things, you show by your acts that you are not from the Lord."; however it is very interesting that the Lord says: "I am still your God who made this and this to you, remember it". This approach is much more affirmative - it makes the person look to the Lord and not to himself.
The Lord reminds idolatrous Ephraim that He loves Ephraim, but He also punishes:

7-12
“I’ll charge them like a lion,
    like a leopard stalking in the brush.
I’ll jump them like a sow grizzly robbed of her cubs.
    I’ll rip out their guts.
Coyotes will make a meal of them.
    Crows will clean their bones.
I’m going to destroy you, Israel.
    Who is going to stop me?
Where is your trusty king you thought would save you?
    Where are all the local leaders you wanted so badly?
All these rulers you insisted on having,
    demanding, ‘Give me a king! Give me leaders!’?
Well, long ago I gave you a king, but I wasn’t happy about it.
    Now, fed up, I’ve gotten rid of him.
I have a detailed record of your infidelities—
    Ephraim’s sin documented and stored in a safe-deposit box.

The Lord is the One who gives life and death as He pleases. Salvation comes from the Lord and not from a human king. The Lord wants Eprhaim to repent and seek the Lord because He is the source of life.

13-15
“When birth pangs signaled it was time to be born,
    Ephraim was too stupid to come out of the womb.
When the passage into life opened up,
    he didn’t show.
Shall I intervene and pull them into life?
    Shall I snatch them from a certain death?
Who is afraid of you, Death?
    Who cares about your threats, Tomb?
In the end I’m abolishing regret,
    banishing sorrow,
Even though Ephraim ran wild,
    the black sheep of the family.

    
Theses verses appear in 1 Cor 15, when Paul speaks about ressurrection: "Who is afraid of you, Death?". Here, the Lord may bring life to Ephraim. But in the next verses we read:

15-16
“God’s tornado is on its way,
    roaring out of the desert.
It will devastate the country,
    leaving a trail of ruin and wreckage.
The cities will be gutted,
    dear possessions gone for good.
Now Samaria has to face the charges
    because she has rebelled against her God:
Her people will be killed, babies smashed on the rocks,
    pregnant women ripped open.”

The Lord is the One who brings death too.
So, we ask: "life of death to Ephraim?"

Hosea 12: The Lord wants Israel, although Israel doesn't want the Lord.

Israel is doing good in her own eyes, saying "I am rich", although far from the Lord.

7-8
The businessmen engage in wholesale fraud.
    They love to rip people off!
Ephraim boasted, “Look, I’m rich!
    I’ve made it big!
And look how well I’ve covered my tracks:
    not a hint of fraud, not a sign of sin!”

The Lord wants Israel back to Him:
    
9-11
“But not so fast! I’m God, your God!
    Your God from the days in Egypt!
I’m going to put you back to living in tents,
    as in the old days when you worshiped in the wilderness.
I speak through the prophets
    to give clear pictures of the way things are.
    Using prophets, I tell revealing stories.
I show Gilead rampant with religious scandal
    and Gilgal teeming with empty-headed religion.
I expose their worship centers as
    stinking piles of garbage in their gardens.”
    
In a similar way, the Lord is the One who came in my life. May the Lord destroy my false gods and make me live depending on Him as a poor lives in tents.