It's recommended that you understand at least 90% of what you read to be able to catch the gist of what is being said, otherwise, you might find yourself spending more time checking vocabulary rather enjoying the story. Reading is a great way to assimilate your language skills. I try to read a page or two of a book to see if I like the style of the writer before deciding if it's a good choice.

My first English book was Season of Passion by Danielle Steel, prolific American writer.- I was only a beginner, but stubborn enough to finish it. It took me 6 months, but the 2-nd book took me only 2 weeks. I would go for Coelho.

If you’re worried about difficult language, the “Alchemist” would probably be the easiest, as it would be a fairly recent translation from the (relatively recent) Portuguese original. Hemingway’s work is not as “ancient” as some native speakers apparently believe, but it isn’t necessarily the best language for an ESL student. The third selection is the oldest of all, and while I haven’t read it, the language is probably not the most relevant to the typical ESL learner’s needs. But in the end, maybe you could read all of them, starting with the easiest one. Good luck!

The language in Hemingway’s The Old Man and the Sea is not quite as difficult as his other works; it’s a great little book! However, there is a lot of maritime and fishing terminology, which makes reading a little slow until at first.

Hemingway is advanced, even for many native English speakers. I recommend buying a book from the New York best sellers list. Books on this list use modern English, whereas classic books (such as those you listed) use an older form of English that’s rarely spoken