I can report that i had similar problems with each of these same writings, though I was tremendously bored by some of them. So in reality, I'm sure I did not get as much out of them as I should have. *guilty smile*
Probably the book I just finished, A Handmaid's Tale by Margaret Atwood.
You're kidding! Atwood is delightful! A Handmaid's Tale isn't perky but it doesn't waste time either. I liked it but actually preferred Onyx and Crake, perhaps because it's more topical and less dated.
I got the gist but deciphering his meaning was pretty damn difficult. I still don't think I got most of it. Kierkegaard is also indecipherable. What is it with Germans?
I agree about the Kant, but I thought Kierkegaard was fairly straight-forward. But Schopenhauer can be a bit of headache at times - his essays and aphorisms are simple to understand but the first book of The World as Will an Representation can be a bit of a headache, and I'm quite sure that 90% of the people who read Nietzsche don't understand him anywhere as near a well as they think they do.