Gregor Samsa awoke from troubling dreams one morning to find that his life had remained conspicuously the same. This in context of the entire book is the actual opening line of Franz Kafka's Metamorphosis. Gregor Samsa, the unfortunate protagonist and indirect narrator of the story has been inexplicably transformed into a bug. But quite truly, Gregor his persona, and the role he plays has remained quite the same.
Franz Kafka's theme of isolation is very thick in this novel. Driven by himself and by the needs of others to work at a job he hates, Gregor is in fact a very lonely, remote individual. Before his metamorphosis Gregor's isolation was apparent mostly in his occupation and stature in society: he was appreciated by his family and mostly adored by his sister, Grete. After he finds himself turned into a bug, Gregor's isolation expands as he begins to accrue the resentment and disgust of others closer around him. This includes Grete, the sister who he so dearly loves. .
There are additionally some themes of materialism in Metamorphosis. Initially after the change, Gregor's family including his mother are close to him, in grief or even disgust. However, as time goes on and Gregor's change has a more lasting impression (financially), his family truly begins to distance themselves in search of material stability.
Kafka's tone in this novel is decidedly calm. He treats Gregor with a certain amount of sympathy, and since the story is basically told from Gregor's vicinity, Kafka treats the Samsa family with increasing alienation. Gregor's father is at times violent, and Kafka treats any negative reaction to Gregor with a certain amount of cold indifference. What the reader sees mostly is the concept of hiding and seclusion.
It could be said that Metamorphosis moves from page to page in chronological movement, but this is not exactly true. Some of the very first introspection of the novel is done in the form of Gregor's review of his past and the quality of his life.