A free program for Android, by Navneet Education Limited.
Navneet DigiBook is the most user-friendly way to study. Not only do you have all the materials in one place, but you also have the entire course in an interactive video format, which makes studying much more fun and effective.
You can also download all of your course material for a particular subject, and access it from anywhere, even without a Wi-Fi connection.
You can choose the best format that works best for you, and you can even download all of your content in an offline format, which means that you won't be charged for data usage.
The best thing about Navneet DigiBook is that you can study for free.