What is the ebooks sales model?

Ebooks are primarily sold in collections to academic/corporate research institutes, where subscribers are able to download an electronic version of the book as part of their subscription—this model is great for students as the book collections come complete with perpetual access, are DRM free, and we do not impose a concurrent user limit, meaning researchers can access the content on whatever device they like, 24 hours a day! They are also available to purchase in both electronic and print on Amazon and other online retailers.