The Trial does deserve the term mindfuck, I think, both because of the story and because it upends the notion of what most people expect of a novel. Kafka's other words are weird and wonderful and not nearly as hard to read as some seem to think, but if you've read The Trial, they're not very mindfuck-y, and that's a big problem with a list like this - each book you read that is still a mindfuck will make a lot of the rest seem pretty pedestrian (though often still good).