Few works of literature in the twentieth century generated as much discussion, imitation, and, yes, confusion as Kafka's 1915 The Metamorphosis. An analysis of it is a daunting task for even the most intrepid of literary critics. One of the most insightful things I've ever read about Kafka is that he wrote fables or allegories (a fruitful avenue of investigation) without a meaning. Or to put it another way, they are locked rooms with no key. What this means for the reader looking to analyze his work is that it is full of ambiguity and irony.
There are several ways to approach the story. One is to look at its symbolic nature. The protagonist, Gregor Samsa, famously wakes up to find himself an insect. What is the meaning of this? It seems to imply a certain bestial aspect to human nature. As the story progresses, he is gradually shunned by his family and banned to his room. Another approach is to look at Kafka's biography and at his complicated relationship with his father. Is Kafka's alienation from his often overbearing father part of this? While it can be a mistake to use an author's life to look at their book, this does feel significant. Adding to this, one could use a Freudian lens to look at Samsa's relationship with his father, as well as his own humiliation and shame. A final approach is to look at Kafka as a Jewish writer and to see the character of Samsa as a stereotype of hateful Jewish imagery throughout the ages. That is, anti-Semites often characterized Jews as less than human, and here is Samsa as a massive insect, perhaps a cockroach. Adding to this, several decades later many members of Kafka's family would be murdered by the Nazis.