Aside from romance novels, most fiction today begs for rational thought. That is, most books are written with characters who have a mythical sense of foresight, which by large, is akin to the author's all-knowing perspective of the fictional world they've created. While it's important for characters to have realistic thought (since this will greatly impact the direction of the plot), I personally believe it's unrealistic. Without irrational thought, characters might lack a certain kind of hope or motivation that will drive them to success or at least an interesting life. Also, experiencing irrational thought through the eyes of fictional characters can be beneficial under real-life circumstances.