Welcome back from your journey, AnotherCat! The link below lists his works in chronological order and also separates the fiction and nonfiction.
Journey without Maps was indeed his first non-fiction book and was also early in his fiction-writing career so I suspect that his later works were much improved. It was also his first trip outside of Europe so I wonder if he got better at capturing his experiences and weaving them together as he traveled to more places.
https://www.fantasticfiction.com/g/graham-greene/