I did an entire semester on him, and maybe I'm just a philistine but for my money there was very little difference between Before the Law (a short story of ~650 words) and any of his longer works. So if you've read that and The Metamorphosis you know basically all you need to know about his writing.
There are other interesting stories for sure (I'd recommend In the Penal Colony and The Trial as Bones also mentioned), but the themes are very much the same throughout-- which I suppose is why the work Kafkaesque exists.
That one on the image. Metamorphosis is a fun short book that you show you what Kafka is about.
On the other hand, The Trial is a long, heavy book that will make you feel like you have gone crazy. Personally, I can't stand this one. (Though, it's because it's very good on what it intends to do.)
Metamorphosis is the go-to Kafka book. I personally find The Trial the most "kafkian" of his novels, and I love it, but Amerika has a special place in my heart as what defines his literature is trying to find a way out, like a little seedling.
The most boring story ever. A guy wakes up, notices he is a beetle for whatever reason, and is afraid his family might notice. That's it. Why anyone would waste paper on printing this shit is incomprehendable.
The guy who's partly responsible for feeding his family can't do that very thing anymore and notices that he basically lost all value to them (they start treating him like shit until he dies). If you want you can say its a book about failing to fulfill gender expectations and about why a patriarchy also is bad for men. About people loving him for what he's doing, not for who he is, and that love eroding as soon as he can't do that anymore.
I saw a really neat video a while ago that talked about this book, and he interpreted the story to be about disability. You go from being the breadwinner supporting your entire family to suddenly you can't work nor enjoy your hobbies, people don't want to look at you and you feel yourself to be a burden upon everyone. Your loved ones take care of you through a sense of guilt and because to not would be neglectful but the level of care might never actually be as much as it should be. The author of the video (I wish I could remember the name of the channel because he had a wonderful voice, writing style and art style) also proceeded to point out that everyone will either die young or themselves experience disability, so it's also a story about what you will become some day. One day you too will turn into a beatle, struggling to get out of bed, unable to work and relying on others to cook and clean and care for you
Because some people can feel the guy who got turned into a Beetle. And it's sufficiently sad and disorienting to be interesting to read.
You just don't seem to ever feel Gregor.
To me Goethe is far less interesting, even with Dürrenmatt I question if he might be more boring.
I'm not sure I can say what the difference is between people that like and dislike Kafka, but I have a friend who also thinks Kafka to be boring and another who like me quite likes Kafka, when compared to other classics, and in some ways that are hard to pin down we just seem to think differently.
So much so that the guy who doesn't care for Kafka at times seems like a bumbling fool and at others like a sage of wisdom, he definitely isn't either of those outright, but our knowledge, our neural pathways might just be different in such a way that even though we are friends and close in age, social and economic strata(and so on), we percive and think fundamentally different.
Why should anyone feel with this Gregor? It is just a story, and a horribly bad one to boot. In a story that is good, capturing the mind, etc, I can easily see to feel with the characters, but this story does simply not warrant wasting any more thoughts.