The Assimil digital books (or ePub) may be read on an Android or iOS tablet or smartphone, or on a macOS or Windows PC.
You can use the free app  Adobe Digital Editions  (for Windows, macOS, iOS and Android) or the iBooks app (macOS or iOS), for example. On your Android device you can also use the Lithium app.
To read these files on your iOS device, you must go through iTunes on your PC to transfer them to your device. They cannot de downloaded directly to your device.
The apps we are suggesting are not the only available ones capable of reading ePub files. You can use the app of your choice. But be aware, not all of them can read the audio recordings contained in our enhanced digital books.