As an English learner, I found Oxford "Bookworms series" and "Dominoes" very useful to enhance my reading skill and my English vocabulary.
For example, about Bookworms series, each book in the series is graded based on the grammar and the count of the headwords the reader needs to know. So as an instance a learner would know that he/she can read books graded 'stage 4' or lower.
I am a beginner in French and wonder if there are good reading materials – like what mentioned above in English – for learning French.