To listen to an audiobook offline you will first need to make sure the audiobook is downloaded to your device- to do this simply open the audiobook in the Glassboxx app on your device. Once this has been done, if you would like to access your audiobook offline in the future, then log in to the app while connected to the internet and then you can switch your device to aeroplane mode or to an offline setting while still remaining able to access the audiobook.