I am really confused about the purpose of The Breast. What are its themes and what are the main ideas the author is trying to get across?
One way to understand The Breast is to look at other texts. Most importantly, one should read and study The Metamorphosis. Knowing Kafka's influence on Philip Roth, and comparing David Kapesh's situation to that of Gregor is essential to recognizing meaning in Roth's novel within a context of a greater literary history. Similar to Gregor Samsa, Kapesh experiences a sudden, complete transformation that he is not at all equipped to deal with. In both cases, the men become something unacceptable in society: Gregor as a cockroach, David as a six-foot breast. Both tales become an attempt to define humanity, & how we determine our identities. Can we accept ourselves once our physical nature is no longer human? Can others still treat us as humans?
One other aspect to consider is Roth's writing style and background. He is a satirist, and his novels are often filled with dark humor and painfully real situations. He also seeks to define the Jewish experience in America. One of the main ideas of The Breast is Kapesh's inability to accept what has happened because of his background; raised as a middle-class Jewish-American, this is so far out of his realm of experience as to be incomprehensible. But knowing that Roth employs satire and humor in his writing will enable you to see the entire premise of the book as a metaphor for loneliness and isolation in modern life, rather than just about some guy who turns into a breast overnight.