""I love you". Why is that the most unoriginal thing we can say to one another is still the thing we long to hear?"
In a discussion about cliches of love, this is one of the thoughts that come up. This expression of love may be simple and unoriginal, but, sometimes, the beauty is in simplicity. Despite criticizing the cliches of love, the narrator has apparently been roped into this one as well.
"Written on the body is a secret code only visible in certain lights; the accumulations of a lifetime gather there."
The line that contains the novel's title and reveals the main message - that love is finding someone who sees you, who can read your story and merge it together with their own. Thus, the narrator says that Louise has translated her/him into her own book.
"Why is it that human beings are allowed to grow up without the necessary apparatus to make sound ethical decisions?"
The narrator is conflicted in making the morally right decision when it comes to falling in love with Louise, who is a married woman. At the same time, the narrator must confront being with another person, who might get badly hurt if the choice is Louise.