Hello,
I think audio books can be very useful for learning a language. It is good to have a text, too. It is possible to use graded readers for learners of English. They are available from beginner´s level to advanced, accompanied by a CD. You can choose between American and British English. It offers many ways how to practise English. For example when somebody needs to develop listening skills , he or she can read a part of the text, next time it is possible to join reading and listening together and repeat it as many times as needed, then a learner tries to do a listening only. It is possible to build a confidenc in listening. We can use graded readers for developing other skills - speak or write about the text with our own words, learn new vocabulary, train pronunciation while reading aloud etc. There are many variations how to work with them.