It is in the Bible to help God’s people relate to those whose only perception is “under the sun,” and to win such folks to a more truthful and satisfying outlook on life. The best way to apply the book is to help people grapple with the despair of materialism and naturalism, and to win them to a God’s-eye view of the heavens and the earth.
In my observation, Ecclesiastes is second only to Revelation in the number of competing interpretive approaches available to readers of the book. It offers a great case study in how perception can drastically affect both interpretation and application. This fact ought to motivate us to be as meticulous as possible in observing the text within its context.
I’ve found interpreters of Ecclesiastes to fall into three general categories, though there are subtle distinctions of flavor even within each category. For an excellent and thorough review of interpretive approaches to Ecclesiastes, along with a careful analysis of the text itself and its place in Scripture, see this helpful (though lengthy) article from the Kerux journal.
Approach #1: The Cynic
This first approach seems to be most common in the academy, where scholars conclude that the text of Ecclesiastes, by and large, is neither orthodox nor commendable.
A conservative proponent of this approach is Tremper Longman, who sees Ecclesiastes as having two voices. The most air time is given to the Cynic, as most of the book is an extended quote of his cynicism (Eccl 1:12-12:9). The outer frame (Eccl 1:1-11, 12:9-14), however, refers to “the Preacher” in third person; therefore it was composed by someone else, who is evaluating the Preacher’s message. This outer frame is the only place in the book where we find an orthodox, praiseworthy message.
Other flavors of this approach suggest that the frame narrator is just as cynical as the Preacher is, and therefore the message of the “frame” is just as suspect as the rest of the book.