I finished The Metamorphosis, and I'm about halfway through both The Castle and The Trial. I'm finally learning what the word "Kafkaesque" means. My definition would involve layers of obscure, contradictory, hellish bureaucracy that suck people in forever, though I'm still not sure that's the whole story. The concept of Catch-22 is very much derivative of this idea.
Sometimes it's quite humorous, like when K. is meeting with the council chairman of the village who speaks of a legendary bureaucrat named Sordini who is known chiefly by the thuds coming from his office from large stacks of files falling over--yet the council chairman insists that he is infallible. The bureaucrat's logic is the circular version commonly seen at police stations and the like--Kafka was really ahead of his time.
Still, I find his prose often irritating. Everyone, including K., argues constantly in this dry, clinical way that betrays little emotion though they often describe becoming upset. In fact, this is why I am halfway though both The Trial and The Castle--I switched to The Trial in the hope that it would be a little more interesting. Sadly, it's much the same. I'm hoping it will grow on me, but for now, I'm not very impressed with actual writing.