If you do NOT want to read the e-book on an e-reader:

You need e-book reader software if you want to read an e-book on a tablet or smartphone. For example, download the Bluefire Reader from your app store to your device. Then download the book. You can download e-books that you have purchased on kosmos.de via the link in your user account. Open the e-book with the e-book reader software.

If you use an iPad/iPod or an older iPhone, transferring data via iTunes is the right way. This is described here:

https://support.apple.com/de-de/HT202075

In this case you also need e-book reader software. The link to the reading program Bluefire Reader for Apple:

https://itunes.apple.com/de/app/bluefire-reader/id394275498?mt=8

The link to the reading program Bluefire Reader for Android:

https://play.google.com/store/apps/details?id=com.bluefirereader

If you want to read your e-book on a PC or Mac, you also need a reading program.
We recommend Adobe Digital Editions:

http://www.adobe.com/de/solutions/E-Book/digital-editions/download.html