The Book of Ecclesiastes is a commentary on the culture and how we are to live within it. Very much like we saw in Leviticus 19 and 20.
Although nowhere exhaustive, here is a high-level summary of the themes found with this writing:
Chapter 1
Life goes on.
Chapter 2
Man seeks pleasure.
Wise men and fools have the same fate.
Your work will not last.
Chapter 3
Life is full of seasons.
Abba gave man an awareness of eternity.
His work lasts forever.
Without God, we are just animals.
Chapter 4
People are oppressed.
Envy is the motivation for striving.
People with no legacy work endlessly -- but for what purpose?
Two are better than one.
Chapter 5
Watch your step in Abba’s house.
Learn to listen.
Execute your vow.
Don’t be surprised by the poor oppressed, rights violated and justice perverted.
The king is supposed to be a servant of all.
If you love money and luxury, you will never be content.
The more you have, the more the parasites want from you.
Be very careful of hoarding wealth.
All your life you will eat in darkness, frustration, sickness and anger.
Chapter 6
Be careful amassing riches, wealth, and honor for someone else to enjoy.
If you fail to find joy, being born dead would be better than even living forever.
You work should make you content and joyful.
Chapter 7
Build a good name (reputation).
Seek out those that are hurting.
Seek out the wise.
Seek out wisdom.
Avoid gossip.
Be very careful in choosing your spouse.
Good ones are not easily found.
Chapter 8
Submit to authority.
Punishment for evil is not promptly carried out.
Evil people will appear to be getting away with their evil.
But you are to be content.
There is more going on than you can begin to comprehend.
Chapter 9
Everything is in Abba’s hands.
Don’t judge people’s righteousness by what happens to them.
As long as you are alive, there is hope.
Regardless, be joyful and don’t let on when things are tough.
Enjoy your life with your spouse.
Don't use human judgment to judge others.
Just because someone has wealth, power, and/or comfort does NOT mean they are going to win the race.
Wisdom can save a city but you may still be forgotten.
But wisdom is still worth obtaining.
Chapter 10
Remain wise even though fools may be esteemed in the culture.
Wisdom has its way and foolishness has its way.
Do not speak poorly of those in authority.
Chapter 11
Put your wealth to work -- just not for you.
Trust Abba will take care of the return in whatever manner He chooses.
You just keep sowing and reaping.
Don’t waste your youth.
Chapter 12
Eventually this will all crumble and pass away.
13 Here is the final conclusion, now that you have heard everything: fear God, and keep his mitzvot; this is what being human is all about. 14 For God will bring to judgment everything we do, including every secret, whether good or bad.