At McGraw-Hill, we have been an active player in e-book technology dating back to devices like the RocketBook (one of the first e-book readers) that was launched more than 10 years ago. And today, e-books and e-book distribution is central to our publishing and growth strategy.

(from an article entitled 5 E-Book Trends That Will Change the Future of Publishing written by Philip Ruppel, president of McGraw-Hill Professional)

Interesting insight into how a business, science and technology specialist is viewing the evolution of the e-book.  This is quite different to the usual publisher spiel which has mostly focussed on the novel (at least in the articles I have read). There is also a nice explanation why they need to charge more than $9.99 for a book saying

For professional and technical publishers like McGraw-Hill, our e-books cannot stand the low, mass market pricing some consumers think should be applied to every e-book. Our costs are invested in extensive product and editorial development of sophisticated and technical content; the cost of paper, printing, and binding are a fraction of the real expense. And for some very specific and technical subject areas, our markets are much smaller. We simply couldn’t afford to publish the work if it must be priced at the everyday low, low price of $9.99.

The real opportunity for publishers will be to develop e-books that offer the kind of interactive features mentioned above. Our customers will demand interactive books that provide a much better, more informed and enriching experience. For them, the experience (not the cost) is often the primary driver.

as well as raising the concept of in-book purchase for extended or more targeted content, such as
They click a help button, which points them to the publisher site where they can download relevant tutorials about specific formulas for $2.99. They choose the one they need and get a new learning tool, which helps them progress in their class
Worth a read if you're interested in all things e-book/publishing.