Mark Driscoll uses a great illustration that summarizes much of the book of Ecclesiastes.
He says that people are living life with a big can of peaches and no can-opener. We walk around wanting peaches but can't get to them. We are frustrated! God comes to us in our frustration and says, "I have a canopener." Ecclesiastes, as a book to be read with Genesis 3 and the Fall in mind, is wonderfully redemptive.