Could anyone tell me the major themes in "The Metamorphosis" by Franz Kafka?

Whenever we consider a work of literature as complex as
"The Metamorphosis," it is clear that there are a variety of themes that we could draw
upon. However, from my perspective, the three main themes are that of the nastiness of
the world of work, betrayal and isolation and
self-sacrifice.

Especially at the beginning of the story it
is important to be aware of how much Gregor detests his job and is worn down by it. He
bemoans the "strenuous" profession he works in, and the first thing he wants to do when
he wakes up is go to sleep again to try and forget about "this nonsense." He talks about
the conditions of his job and explains how hard they are. He is a man who is unfulfilled
by his job and oppressed by it. Not only that, but it is clear that they do not trust
him at his work, and his boss is quick to come and fire
him.

Betrayal is a theme that is evident through the
transformation not only in Gregor but in particular in his sister. We are told that it
is she that Gregor loves. He is willing to work so hard to help look after her.
Relationships between him and his father in particular are strained, but it is Gregor's
sister that loves him and also tries to look after him at the beginning after his
transformation. However, given this mutual affection, it is therefore a big surprise
that at the end of the story it is his sister that persuades their parents to move on
and pretending that Gregor is not actually Gregor but an insect that is trying to kick
them out of their house. This betrayal suggests that even the closest of relationships
cannot be trusted.

Lastly, ironically it appears that
Gregor led quite an insect-like existence even before his transformation. He led a
lonely, isolated life before his transformation, and this is continued afterwards, as he
is unable to communicate with anyone as an insect. Note too the irony in that Gregor as
an insect can only hear what others want and desire and cannot communicate himself.
Before his transformation, he seemed to be a character who would always try and meet the
needs of others rather than his own needs, so perhaps this is
appropriate.

Overall, this story paints a bleak picture of
human existence that is marked by isolation, alienation, dissatisfaction and
betrayal.