The irony of existence
One of the first themes in the book is to focus on this irony, the ironic nature of reality. Especially in the word "nature," this irony is evident. The idea of "nature," that the universe exists according to principles and rhythms, is fundamentally outside the grasp of the human intellect. It is ironic and absurd that the universe in which humans exist should be so genuinely unfathomable in its perfect order. Hesiod shows this irony especially well in his depictions of the unfolding order of the universe through the intermarriage of gods who spontaneously occurred without being created.
The irony of order and chaos
Another interesting irony concerning the metaphysical reality of the world is that very often in this book, order is contrasted against chaos. Sometimes, order creates a new element or dimension in reality, which causes the entire order of reality to experience a shift. For instance, when Zeus is crowned as high king of the gods, he marries all the women he pleases, which means that his authority is integrated into the next generation of gods. Ironically, this chaotic element is ultimately responsible for the order of our reality, in Hesiod's imagination.
The irony of life and loyalty
There is an irony between life and loyalty in this book, because life is shown to be a fertile, explosive idea, against which the arbitrary loyalty of marriage is not sufficient. In the gods' realm, the standard is "be fruitful and multiply," which for characters like Zeus, Aphrodite, or basically any of the gods in that generation, means to have sex with anyone who will. The literary effect of this ironic element is that reality is shown to be a flourishing, something that can breaks certain rules strategically.
The irony of capricious deities
The gods are shown to have absurdly human qualities (anthropomorphism), and those human qualities are capricious. Therefore, although the gods are supposedly the very pillars of the human experience of reality, they are capricious and mischievous. Not to mention that their violent tempers are unimaginably severe, such that their capricious quality leads the theologian to fear.
The irony of human life
There is no examination of the heavens which is completely detached from human interests. Therefore, this book of gods is ironic, because clearly the point is not to learn about the gods, but to learn about the humans. In a way, Hesiod accomplishes some goal ironically, accidentally even. He accidentally attempts a full psychological model of the human mind, because he exhausts his imagination trying to explain the unexplainable reality of this human life.