Nietzsche Vs Twain. Which one first?

On my Goodreads wanting to read list, I have two books from these beautiful writers.

“Twilight of The Idols/The Antichrist”

“Letters from the Earth”

The most difficult book I’ve read in last 8 months was Tender is the Night by F. Scott Fritzgerald.

I’m trying elevate my mind with more challenging my books but I would like to understand the material.

Which direction should I go?