Ecclesiastes
People disagree about what the Book of Ecclesiastes means.  Some people think the book is very pessimistic, saying "all is vain", "there is nothing new under the sun."(Chapter I), and "I looked again at all the injustice that goes on in this world. The oppressed were weeping but no one would help them. No one would help them, because their oppressors had power on their side. I envy those who are dead and gone; they are better off than those who are still alive. But better off than either are those who have never been born." (Chapter 4)  Other people think the book says that even though life is hard and we will all die someday, we should just enjoy God's gifts.