To explain usage of the app, we can create a small tour for first time users.
In Home Screen, we can add popups to show the three filtering options at top right. Switch Language, Sort Books, and Search function.
We can then show a popup to select a book from the list. After that, we can show the category screen, Library, and Settings.
There should be also an option to skip in each step.
The Myne app has some tours for reference: https://github.com/Pool-Of-Tears/Myne/