On carbon footprint she may have a point, although arguably every book is a little chunk of carbon sequestration. CO2 enters the atmosphere when things are burned, which books usually aren't; with less demand for paper, there may not be an economic incentive to plant as many fast-growing trees. It's true that their production and transport consumes a good deal of energy that e-books don't, however.

I don't think you're old. I rely heavily on the 'active reading' tools available via computer, such as searching, hyperlinks, and so forth. But that sort of reading is more at the research end, where you know roughly what information you want and any learning you do along the way is relatively shallow. If I'm reading passively and trying to gain a deep understanding of the characters or concepts being explained by the author, then I still very much prefer a book, even though I may flip back and forth frequently if it's technical in nature. I also find it more productive to write notes by hand in this mode, rather than type or cut and paste. Of course, this relies on a good author, whose narrative or didactic approach the reader can trust.

Arguably, this is irrational. I do like the smell of (well-kept) books, the texture of the paper and so forth; it pains me to see someone mistreat a book or snap the pages when they don't like what they're reading. Some of this is nostalgia (books were an avenue of escape from a difficult environment growing up), and some is a conditioned reflex. When I sit down to study a book, these sensory cues help to shift my brain into study mode and ignore distractions. This is partly because of the limitations involved. If I need to put down the book and walk back to the shelf or to the computer to check the meaning of a word, or answer some peripheral question it's a time-consuming interruption; I must decide between accepting the inconvenience, postponing it until the end of the reading session if possible (and then checking several things at once), or staying put and just thinking the problem through on my own. Proceeding without filling the gap in understanding is generally a bad idea; I'd rather re-read material from earlier than build knowledge that's structurally unsound. Working the problem through is obviously slower than looking something up, and the knottier the problem the more important it is to check the quality of one's solution later. On the other hand, one's own brain is ultimately portable, and solving a problem exercises both short- and long-term memory better than consulting an oracle. It's like eating; packaged or processed food is very convenient, but too much of it weakens the digestion. Although computers and ebooks have great unrealized potential for education, they should probably not be the primary reading medium for kids, any more than instant snacks or fast food should be considered the cornerstone of a healthy diet.

E-books have three problems from my point of view. Cosmetically, the pages are too small, the text is too large, and the reading surface is too grey. I like high-density text but so far only the iPad gets close. Functionally, I like the convenience of digital storage/retrieval, but would actually like the option of an 'exclusive' reading mode which locks me out of search, dictionary lookup etc. If there is no inconvenience to using such resources, then I have no economic incentive to puzzle over something and work it out myself, whether by mental effort or searching back through the text for something that was overlooked on a first reading.

And conceptually, there's a McLuhan problem: 'the medium is the message' in the sense that the reading device is the gateway to knowledge, and can be locked or restricted. Books become something less than independent works of creativity and scholarship, and more generic 'content' which must adapt to the reading device. Many subtleties of typesetting and reading order are lost along the way, along with the publishing income from older literary works, which to some extent subsidized the publication of newer writers. Books have less of an individual identity with which to attract readers or retain their affections. More importantly, as the market for reading devices matures they will necessarily compete on features; whereas a paper book's literary value is independent of the binding, the content or availability of e-books may become a function of the device on which they are read, with owners of fancy devices enjoying a much wider selection of reading material. Last but not least, digital technology can facilitate censorship as well as distribution. Although the ability to correct errors and update reference material in a digital text is a great advance in many ways, the ease with which newly-unpopular truths can be retroactively deleted should give pause. We've already seen one example of this on the Kindle, where copies of 1984 disappeared overnight due to a copyright issue; recent events involving Stuxnet and Wikileaks suggest a very near future in which malware targets not systems in general, but specific data or configurations incompatible with others' interests. In the literary context, deletion of any material suggesting that we have not 'always been at war with Eastasia' or that 2 + 2 = 4, for anyone who can not produce documentary proof of a 'need to know.'