Just finished Black Amazon of Mars by the late great Leigh Brackett.
Nothing groundbreaking or thought provoking, but really fun and pulpy all the way through. The oldest piece of fiction I’ve read (save for snippets of The Odyssey and Inferno) is The Martian Chronicles by Ray Bradbury, so perhaps I need more experience to gauge this correctly, but Black Amazon feels way ahead of its time.
Next up is Superman: For All Seasons by Jeph Loeb and Tim Sale.