There are so many humorous one liners and puns in this novel, and it's easy to see them and say "Ah, this is a funny book," without questioning their appearance in the first place. Why does Benna resort to humor? At the end of the novel, when Benna decides to chill at her brother's apartment for fear of suicidal loneliness, there is a sense in which her jokes are suggestive of something dark and horrible. She wonders what kind of suicide notes her dog might leave her. Given her avoidance problems and her willingness to play pretend instead of facing reality, that language sounds very scary. It sounds like psychological project, like maybe she's hiding a deep, dark suicidal depression.
This is certainly the implication of her decision to go stay with her brother. She literally navigates life by finding one person at a time who can care about her well-being in some way. Sometimes they're casual lovers, sometimes they're her imaginary friends. So why in the end does she feel that she absolutely must find someone to be with? Perhaps the joker has run out of irony, and suddenly the threat of real isolation is also the threat of emotional failure and collapse.
All in all, the story is a brilliant expression of existential loneliness. The way Benna faces her daily life with a sense of pep and joy in spite of her unbearable loneliness is heroic and vulnerable, but her decision to play pretend with imaginary friends might be an indication that she is not well adjusted to true community. Perhaps the reader might consider Benna to belong to the type of the very funny, very intelligent person who is secretly suffering. She's like a stand up comedian or something, fighting off suicidal pain with jokes and levity. And it works, for a long while, but eventually one must hope for a deeper peace and a sense of hope for Benna.
