If a library was burning to the ground, and I could only save a book on a shelf, a digital photo of the book and its pages, or the book digitally transcribed, then which would I choose? Obviously one could take the book and derive the other two from that with some amount of work. Excluding this possibility, my first instinct is to choose the book digitally transcribed. This is not because I prefer to read books digitally, in fact the opposite is true. However, having a digitally transcribed version of the book means that more than just I can read it. This can be distributed throughout the globe with ease due to the internet, on sites like Google Books. While many books are enjoyable to read, I think that the spread of knowledge is their most useful function, and by that logic the digital version is the most useful.
One might argue that having digital photos of the book could also be distributed just as easily. However, with a photo it is much more difficult to change the format of the book. One can read the text in the photos, but without the use of software to automatically scan the photos into text form, one would have to manually scribe the entire book into a text document. However, a digitally transcribed version can be easily transferred from PDF, to Word document, to website form with only a few keystrokes.
Not only can format be modified, but so can the format and presentation. One can easily extract excerpts, and even adjust aspects like the font. While these seem negligible, they can be used to set the tone for a piece of literature. So while I do believe that there is a certain je ne sais quoi that come along with reading a paper book, I think that the utility of a digitally transcribed book is far more important.