Many of the works are short so they can be read on a single flight, including titles that cover management, marketing, and other business topics. There are also summaries of prominent pieces that are selected by professional editors.
The airline is saying that this digital library is a first for the industry, and they could well be correct. The only similar program I can recall was Virgin America's RED in-flight entertainment system. When RED was announced in 2007 Virgin America promised that it would have a section for ebooks (in addition to the other media available at launch), but that part of the platform had not been deployed when I flew on Virgin America in late 2012.
You can find the Sky Library app in Google Play and iTunes, and you can find out more by visiting SkyLibrary.com. While the press release suggests that the Sky Library is available to Miles & Smiles members, the website appears to be open to all.