I added more books to the Readable Bookstore, including some that are good for beginners (Frog & Toad) and high-beginner readers (The Littles). If you like The Littles, there are many more books in that series. Both series are old, but many people still love them. You may be able to find them at a used bookstore in the children’s section.
If you want to visit the Readable Bookstore later, the link is on the right side of the main Readable Blog page. It says “Books for Learning English: Readable Bookstore.” I try to add to it when I think of a good book for English learners (or teachers). If you buy a book through the bookstore, I get a small amount of money from Amazon. But you don’t need to do that. You can just use that page as a useful list of books.