The misnomer
The book is mis-titled. A more accurate title for the book would have been, "The Existentially Horrifying Science." The book is about the death of God and the horror of true "freedom." It's a work of nihilism and obscurantism.
The religious atheists
So much of Nietzsche's The Gay Science seems not to be a rejection of religion, as many atheists might have claimed. But rather, Nietzsche seems to be criticizing the hypocrisy of atheists themselves. He demands an answer for this question: Why say you don't believe in God if you're just going to continue on with the same religious assumptions about your own life? For instance, many atheists assume their lives are meaningful and that they have destinies. Why? Nietzsche doesn't allow this hypocrisy.
The irony of God's death
The words "God is dead" are technically ironic, to the point of paradox actually. For instance, if there were a God, he or she would be immortal, one would think. But Nietzsche's God is not a literal "God." Rather, Nietzsche kills the human conception of a god that never existed. The irony in the statement might be the ultimate form of irony in any language. Perhaps Nietzsche has written the most ironic line in human history.
The irony of recursion
Without a sense of a God who is in charge of ensuring order and progress in the universe, Nietzsche is left to conceive of his life in a multitude of horrifying ways. He shares with us one of his nightmares or thought experiments. What if randomly one day, an angel told a person that they were already in hell, and that their punishment was to repeat their life again and again for all eternity? Without a religion to restrict those kinds of beliefs, free minded people are condemned to objective speculation.
The Buddha and God
Everyone and their mother has heard someone say, "God is dead." But not many people know that the first time the phrase ever appeared in Nietzsche's writings, it comes after a description of Buddhism, namely the manner by which people manifested a religion around the private teachings of a dead man. Therefore, he argues, God's legacy will live on in the form of archaic religions for thousands of years until little by little, people start to come to their senses. Ironically, the Buddha's teachings are largely compatible with Nietzsche's teachings. Buddhism and nihilism are two sides of the same coin.
