This Shabbat is שבת חול המועד. We read the book of Kohelet, written by Shlomo Hamelech. It seems to be a reflection by Shlomo of the vanities of life in the physical world.
It is read on Succot because of an important statement made by Chazal. אין אדם מורד בהקדוש ברוך הוא אלא מתוך שביעה, that an individual only rebels against Hashem when he is filled up. If things are going well for someone, and he has plenty of money and comfort, he tends to forget that these are all gifts from Hashem.
Kohelet is read at the most prosperous time of year. Most Jews were farmers and they sold their summer crops at this time. A perspective was needed to remind people not to get carried away with themselves.
Shlomo Hamelech sums up this mundane imperfect world with the final Pasuk: סוף דבר הכל נשמע. את האלוקים ירא ואת מצוותיו תשמור. כי זה כל האדם. In the end, when all is heard, one needs to only fear Hashem and keep the commandments, for that is all that really matters to man.
Joy that comes from material gain is fleeting. The spiritual joy in observing the Torah, is lasting and permanent. The contentment achieved from spiritual pursuits, far surpasses the physical. This is the message of Kohelet. Shabbat Shalom