The main body of the text is ascribed to Kohelet himself.Kohelet proclaims that all human actions are hevel, "vapor" or "breath", meaning "insubstantial", "vain", or "futile", since the lives of both wise and foolish people all end in death. While Kohelet clearly endorses wisdom as a means for a well-lived earthly life, he is unable to ascribe eternal meaning to it. In light of this perceived senselessness, he suggests that human beings should enjoy the simple pleasures of daily life, such as eating, drinking, and taking enjoyment in one's work, which are gifts from the hand of God. The book concludes with the injunction to "Fear God and keep his commandments; for that is the whole duty of everyone. Since every deed will God bring to judgment, for every hidden act, be it good or evil".
Few of the many attempts to uncover an underlying structure to Ecclesiastes have met with widespread acceptance; among them, the following is one of the more influential:
Initial poem (1:2–11)
I: Kohelet's investigation of life (1:12–6:9)
II: Kohelet's conclusions (6:10–11:6)
A: Man cannot discover what is good for him to do (7:1–8:17)
B: Man does not know what will come after him (9:1–11:6)
Concluding poem (11:7–12:8)
The presence of Persian loan-words and Aramaisms points to a date no earlier than about 450 BCE, while the latest possible date for its composition is 180 BCE, when the Jewish writer Ben Sira quotes from it.
According to rabbinic tradition, this book was written by Solomon in his old age.There is an alternative tradition that "Hezekiah and his colleagues wrote Isaiah, Proverbs, the Song of Songs and Ecclesiastes" This probably simply means that the book was edited under Hezekiah, but critical scholars have long rejected the idea of a pre-exilic origin.
The rest of this comprehensive Wikipedia article on the book can be read here.
An extract from BHFA Volume 5
דִּבְרֵי קֹהֶלֶת בֶּן־ דָּוִד מֶלֶךְ בִּירוּשָׁלָםִ ׃
in Jerusalem king David son of a preacher words of
KJB The words of the Preacher, the son of David, king in Jerusalem.
NASB The words of the Preacher, the son of David, king in Jerusalem.
ESV The words of the Preacher, the son of David, king in Jerusalem.
NLT These are the words of the Teacher, King David’s son, who ruled in Jer.
NIV The words of the Teacher, son of David, king in Jerusalem:
A footnote in BHS states that the Greek Septuagint has, βασιλέως Ισραήλ εν Ιερουσαλήμ, "the king of Israel in Jerusalem."