[dmils4]

I run a price comparison site for textbooks, SlugBooks. There are two simple factors which impact slow adoption of digital books:

1) college bookstores. It's a distribution issue. Students are used to walking into the bookstore to buy something. The bookstore is used to selling them something. Digital books hurt that experience so there's an inherent disadvantage to bookstores promoting digital. This is as big a factor as any.

2) price. Publishers think they've priced digital books fairly, because they use the full retail value as their point of reference. Instead of paying $200 for a full retail copy, students will surely pay $100 for a digital rental, right? They fail to understand that digital books are going to be acquired online, meaning there is a greater chance students purchasing these books will be comparing prices. College bookstores which offer digital as an option even compare that price to their other (often more affordable) options, like buying it used. That $100 digital rental is frequently available for less than $60 on Amazon or sites like it.

It's not a feature problem, it's distribution and really bad pricing.

Until publishers pay attention to these things, digital will never catch on (regardless of how much they innovate technology).