A question that also equals to... paper or digital data? As paper could come from natural resources, or includes chemicals, its usage is not really free of environmental implications. Even recycling it, a considerable amount of energy and work are required for the purpose.
Students, one of the sector that does consume more books, might change every book for a digital counterpart. Is even cheaper as the digital device usually costs less than the entire collections of books for a single year.
And with the advent of mobile and handy technology like tablets, smartphones, netbooks, readers and so on, conventional paper should lose presence year after year.
And from the editor's perspective, there's the problem of piracy, but if the population stays fair the considerable production price of the physical support could disappear and then to maintain earnings at a sufficient level.
Moving toward digital, there's an extensive list of benefits and not a lot of issues. Even for those who are accustomed, it's difficult to forget the aforementioned list and remain in the ancient age started millenniums ago. Access in every place, carrying dozens without height, easily shareable to foment culture and progress, get one thousand in ten minutes, with full color images or some innovative animations with access to the network for solving vocabulary doubts or whatever, lesser price and being responsible with the environment.
On the Internet, is really rare not to find free e-books almost all available topic, and it's true that some cities have a great library, but Internet is each day closer to every place and has more potential variety than any other.
Only if you don't know this resource it serves as a nice start! The Internet Archive eBook collections, right now with near six million items.