The irony of young adult life
The portrait of Tristan is one of a young man struggling to appreciate the gravity of adult experience. He is blooming outward from an initial position of innocence, so the book is mainly about the ways in which life is ironic, when viewed from a adolescent, transitory point of view. This irony includes responsibility, maturity, sacrifice, self-control, and other kinds of ideas that mean completely different things to children than they do to adults.
The irony of death
The ultimate irony of adulthood is that although a child wants nothing more than to have their full power, there is not power available to anyone which could save them from the ultimate disappointment: that all human life ends in death. Tristan's romance is a journey to understand the drastic limitations on his life, which ends in the book, by the way.
The irony of a hero
A hero is someone who does all the right things, right? But this portrayal of Tristan shows a hero who does questionable things with mixed motives. So ironically, he is a hero not because he does the ideal thing in every instance, but because he obeys his higher instincts. He is thoroughly human, and his life is valuable anyway. We are invited to celebrate Tristan, although he gets hung up on certain kinds of challenge.
The irony of the plot
The plot is ironic, because it is a Romance by title and genre, but it ends with separation and death. Ironically, this is by design, because it illustrates the perfectly tragic nature of human life. The plot is not about a happy, healthy, powerful person. It is about the decay and death of a state of innocence that Tristan's character represents. He is fully experienced in suffering and death by the end of the book.
The irony of tomb flowers
The final motif of the novel is the use of flowers on a grave. The author notices that although people often lay flowers over a grave as a sign of remembrance and mourning, the earth also yields flowers out of dead bodies. The earth itself seems to be illustrating its appreciation for their lives, in an ironic, painful way that might just be King Mark's wishful thinking. Ultimately, the question of death is the value of the human lives that came before it, but the dirt itself gives new life regardless.
