I love the book but haven't yet watched this movie. I've only seen Citizen Kane from Orson Welles but I thought it was a masterpiece. I expect that I will enjoy this adaptation of "The Trial".
My question is where the hate comes from. I expect that it comes from the surreal nature of the original story.
I wouldn't call the film surreal, because that will have people expecting pink unicorns and slicing eyeballs. It is a nightmare of the bureaucratic sort, where everything is over-extended and over-detailed. In this it is a faithful adaptation of the book, though some chapters are shuffled around.The emphasis on sexual impropriety is also not what I remember from the book, though my last reading was a couple decades ago.
Given the film diet most people are fed, I wouldn't expect The Trial to get a fair shake. The aesthetic is simply too different. The emphasis is on mise-en-scène and circular dialogue rather than character development or moral. besides all this, the pitch black humour is likely to be lost on most viewers.
But it's a brilliant film.