His well-known works include Notre-Dame de Paris (in English generally The Hunchback of Notre-Dame) and Les Misérables. In terms of graded readers, Penguin/Pearson have The Hunchback of Notre-Dame at level 3, and Les Misérables at level 6. Oxford Bookworms have Les Misérables at level 1 
Hugo could not speak English, despite living on Guernsey for 15 years (though Guernsey is Anglophone today, then it was Francophone). He is alleged to have said "When England wants to chat with me, let her learn my language," - though presumably he said this in French.