going through the list, they all have benefit to your education and literacy but many of them are a chore to get through or very boring to read.
I'd have to say Mark Twain is an easy author full of wit and satire. I am personally a fan of Henry David Thoreau, but I wouldn't recommend him if you're looking for easy.
If you're reading Herman Melville I'm going to assume you're reading his most popular book, Moby Dick which I think is a great story and is engaging. I'd still pick Mark Twain.
I'm not a big fan of poetry, personally, but Robert Frost and Emily Dickinson are both REALLY easy to read and understand.
A few books that I think you should steer clear of are: Nathaniel Hawthorne's Scarlet Letter as it is a boring read and the moral and plot are both terrible and there's no real value to it at all, Ayn Rand's Fountainhead as it is terribly long and boring.
The Great Gatsby by Fitzgerald I'm kind of on the fence about recommending. When I read it I felt no attachment to the characters, I felt they were all twats and I hated them, and there was no plot and nothing was really going on but then when I finished it occurred to me that though I didn't think I liked the book I couldn't think of a single book I've read that was better.
A lot of these authors I have not yet read, but I want to say again that this list is FULL of great literature and anything you pick from it is going to be good for you.