Over the next five years, digital textbook sales in the United States will surpass 18% of combined new textbook sales for the Higher Education and Career Education markets — a more than $1 billion market, according to a new study by educational software company Xplana.

The increase in e-textbook sales will be driven by a series of hardware and technology trends, including:

* Success of the iPad and the tablet form factor in general
* Increased sales of netbooks and the success of Chrome OS for netbooks
* Proliferation and continued popularity of e-reader devices and e-reader platforms
* Growth of the smartphone market

More info: The Xplanation