It is important to first realize that "The Metamorphosis" by Franz Kafka was first written in German. I am assuming that you are reading an English translation. This creates a problem when analysing language. When we discuss diction, imagery, and syntax, we do so based on connotations associated with the words we read. When a work is translated, some associations are lost, and it is much more difficult to determine the author's intent.
What we can say, from the English translation, is that the language is direct yet extremely descriptive. Kafka is a master of imagery. He creates a clear picture without being overly wordy.