Whatever you are in life, a bitch, lover, child, mother, sinner, saint, hell, dream or nothing in between, the end is the same. The author somehow missed all those vague references to Sheol in the other books, because he indicates that the end is the end and death is permanent and final.
One verse I really do like is the sixth: Also their love, and their hatred, and their envy, is now perished; neither have they any more a portion for ever in any thing that is done under the sun. I wish more people would remember that and just let things go. Or, as the writer says, eat drink and be merry.
Some other advice: always wear white, even to barbecues, keep your hair oiled, find joy in your relationship, despite his earlier misogyny. Work hard at whatever you do. Remember that your life is as governed by random chance and time as everybody else's and no one knows when his number will be up.
Then he tells a little parable about a city that was under siege and a wise man who helped them out, but wasn't remembered for his good advice, and reminds us that wise men are heard better in silence and it only takes one fool to ruin it.