Quote from the book "Варяг. Княжич Варяжский"

Suitable for smartphones, Android tablets, e-readers (except Kindle) and many programs

Development of FB2 format

Accessible from nearly any device

Works on any computer

Works on any computer

Opens in Adobe Reader

Optimized and suitable for smartphones

Suitable for Android apps

Suitable for iOS devices (iPhone, iPad, iMac) and most reading apps

Perfect for iPhone and iPad