Ecclesiastes is Koheles in Hebrew, may be questionable in its context first hand. But, its essence is undoubtedly critical to the whole of the Holy Bible. Ecclesiastes by King Solomon, teaches the true purpose of life based on his own experience.

Material blessings obtained (as it may appear) must be used for G-d’s intended purpose, not against Him or for your own selfish gain.

Man’s whole duty is to fear G-d and keep His commandments.