Reading is a great way to improve your English at any age. (Some people think reading lots of easy, fun things is the best way to improve your English.)
Here is a new website that may be good for reading English: BeeOsasis.com: Big Things in Basic English. They have 6 different reading levels, from “very easy” to “near native.”
A professor started the website, and it seems different from other ESL websites. It’s very “clean” and nice to look at It doesn’t have a lot of annoying ads like most other sites. Most of the other free reading websites I’ve found have a lot of spelling mistakes and grammar errors, so I haven’t told you about them. This one is good and doesn’t have many mistakes! However, the website is still pretty new, so there aren’t a lot of stories yet. You can join the website, and I hope they’ll add more to read in the future. It’s free to join. (By the way, if you are Japanese, you can use the website in Japanese, too. Of course, the stories are still in English!)
Now, I think the levels are a little confusing. In my opinion, many of the articles marked “middle” are actually “advanced” due to the use of idioms and other difficult vocabulary. Just don’t worry about the levels. If you know you are usually an intermediate-level reader, but you need to read “easy” stories on this website, it’s OK. These levels are not the same for each person. Read things that are comfortable for you.