Fun and immersive
This app is for those who want to seriously get into French and stay there. Yes, Duolingo is free, but it lacks the depth and immersion to hook most people for the long haul. I think the asking price for the app (~$30/mo) is very fair considering the level of immersion and tailored lessons that you receive. You will learn so much about the language, people and culture, both French and French-Canadien.
The app itself works flawlessly on my iPhone 5.
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Learn French with Le Monde