Books I'd recommended are:
Animal Farm by George Orwell
Winds in the Willows by Kenneth Grahame
The Giver by Lois Lowry
They are usually given to children but in my experience, they are very good reads for adults too. They aren't too complicated and are interesting.
You should also try non-fiction books, which is my favourite.
I've also heard that listening to podcasts can help with speaking english.