Quest to prove masculinity
One of the major themes in this book is David's quest to prove his own manhood. The book begins with David remembering his first sexual encounter with a boy whom he later bullied to feel "like a man." Soon, the narrative shifts to his alcoholic father's house, and the focus becomes his father's need to see his son as a real man.
The entire book revolves around the idea of the "real man", and the relentless need to be one. David strips himself of his identity just to feel secure in his masculinity.
Quest to find oneself
Another important theme in this book is David's quest to find himself. He decides to leave for France after the accident to explore himself, and finds himself penniless for a year. Somehow this quest always leads to him wanting to be a man, and the idea of masculinity becomes an important part of his identity.
Relationships
Another important theme in this book is that of relationships. David's life is characterized by odd relationships. He seems to be constantly conflicted between his sexual relationships with men and those with women. This element forms the narrative of the book into one which explores the instability in relationships.
Homosexuality
A recurrent theme in this novel is that of homosexuality and the conflict between homosexuality and the idea of masculinity. David constantly explores his homosexuality in patches, and then follows it up with something he does to prove his manhood.