Humorously, generations of English translators have gotten more and more carried away with this literal (and incorrect) version of Gregor's transformation, and have actually rendered Ungeziefer as "cockroach," "dung beetle," "beetle," and other highly specific terms. This has become such a common misconception, that English speakers will often summarize Metamorphosis as "...a story about a guy who turns into a cockroach." Despite all this, no such beast appears in the original text.
Warning: Wikipedia contains spoilers.
The story is sometimes comic - for example, near the start, Gregor's main concern is that, despite what has happened, he must nevertheless get to work on time.
However, most of the story revolves around his interactions with his family, with whom he lives, and their shock, denial, and repulsion. Gregor is unable to speak in his insect form, and never communicates with his family at all. Horrified by his appearance, they take to shutting Gregor into his room, but do try to care for him by providing him food and water. Nevertheless, they seem to want as little to do with him as possible, and Gregor's father nearly kills him when he emerges from his room one day.
Confined to his room, Gregor's only activities are looking out of his window, and crawling up the walls and over the ceiling.
Devoid of human contact, one day Gregor emerges again, hoping to get his much-loved sister to join him in his room and play her violin for him, but her rejection of him is total, when she says to the family:
The Metamorphosis is open to a wide range of interpretations; in fact, Stanley Corngold's book, The Commentator's Despair, lists over 130 interpretations. Most obvious are themes relating to society's treatment of those who are different. Other themes include the loneliness of being cut off and the desperate and unrealistic hopes that such isolation brings.