As I see it, the hardware coming our way is going to expand the definition of what a book is beyond static text and pictures and distill the meaning of “book” to its purest essence: packaged information. Thus I would argue that in the long term, “Book” will come to mean *primarily* electronic information formats (plural, yes; I do *not* believe in one-size-fits all straightjackets, ePub or no ePub) and that these packaged formats will acquire many of the interactive features of the formats we now consider software. Specifically:

Children’s picture Books:

Exhibit A: Mattel See-n-say
http://en.wikipedia.org/wiki/See_'n_Say
Exhibit B: TI Speak-n-Speak
http://en.wikipedia.org/wiki/Speak_&_Spell_(toy)
Exhibit C: Jumpstart Educational Kidware (and competitors–they are Legion, no?)
http://www.jumpstart.com/aboutus/aboutus.aspx

For well-on fifty years now, there has been a steady migration of kid educational tools (disguised as toys and entertainment) away from single function gadgets to ever-more-sophisticated interactive applications. The plethora of Kidware on the market these days is one of the strengths of the Windows platform; the fact that these tools are delivered as application software obscures the fact that the bulk of these packages are, in fact, interactive picturebooks. The lack of a standards-based framework for packaging these works in a standard run-time format has forced their Publishers to deliver them as appware (no diferent than the appware ebooks on the iPhone, really) but there is no law of nature that says this state of affairs will continue eternally.
I would, instead, suggest that as ebooks become mainstreamed over the next decade some adventurous outfit will craft a standard framework (analogous to the easy to use and highly efficient HDi Microsot and Toshiba developed for HD-DVD, maybe even *based* on it; it isn’t wedded to optical media or HD video at all: http://en.wikipedia.org/wiki/HDi_(interactivity) ) to deliver interactive multimedia ebooks, thereby divorcing the content from the runtime application. Benefits would be usual; platform-independence, lower development costs, etc.
As for the hardware, I would suggest that once plastic substrate color displays (LCD, OLED, or eInk is irrelevant) are mainstreamed in the next decade, a low cost, kid-focused, indestructible tablet could be built to run these interactive picturebooks on the proposed standard framework. All the necessary pieces either exist as prototypes or are imminent. (I would embed the whole thing in a 1 inch thick lucite slab; lets see the rugrats try to break that!)

Cookbooks:
Once we accept that PC encyclopedias, tutorials, and training applications are in fact interactive ebooks (packaged information, remember?) cookbooks are a trivial implementation for an Apple Unicorn or a Microsoft Courier or whatever the Asus dual-panel reader ends up being. The added value from the interactivity, instant gratification, annotation, multimedia, and extensibility of the ecookbook would make a compelling case for the digital product among non-luddites.
Exhibits A-through-J:
http://cookbook-recipe-software-review.toptenreviews.com/

Coffee table books:

I’m going to date myself.
Back in the 90′s I amassed a colection of a dozen or so “coffee table” CD-ROMs on a variety of subjects. Fun stuff. Most ran 100-200MB in size and focused on subjects like Martial Arts, Space Exploration, Nature, Shakespeare, Mark Twain, etc.
Strip away the CD delivery mechanism and what remains? Yet another pre-existing example of interactive ebooks delivered as appware.
Exhibit A: Isaac Asimov’s Ultimate Robot
http://www2.worldvillage.com/wv/cafe/html/reviews/robot.htm
Exhibit B: Planet Earth HD collection
http://en.wikipedia.org/wiki/Planet_Earth_(TV_series)

The Ultimate Robot is a clear ebook product; it is structured around a collection of all the Asimov Robot SF stories and places them within the context of the science of robotics. But instead of just limiting itself to still photographs, it enhances the package with audio, video, and animations. As a Pre-HD product, the video is low-res, but it shows how interactivity can add value to the coffee table book niche. Similarly, Planet Earth is arguably a coffee table book in its own right; pretty pictures brought to life in your living room. Add in interactivity and, regardless of delivery medium, it serves the purpose of this particular publishing niche.

Now, I know a lot of people have a problem accepting the concept of interactive books but the fact is there is nothing new there; Philips’ aborted CDi is 20 years past by now:
http://en.wikipedia.org/wiki/CD-i

And the MPC CD publishing wave of the 90′s was also ahead of its time:
http://en.wikipedia.org/wiki/Multimedia_PC

But both laid the groundwork in technologies and tools for the modern media-rich web and for the interactive ebooks to come. The technology to address these markets exists today and the economics look favorable; all that is required is for static ebooks to establish themselves first and put pressure on the economics off the printing industry. Both are things I see as inevitable. I don’t think POD is going to be enough to save the mass printing companies and as that industry hits crisis mode in the next decade the publishers of the specialty print products (from coffee table books to comics) are going to see ever-increasing print costs and pressure to move to electronic media.

Eventually, every form of packaged information *will* be available in digital form commercially. Doesn’t mean all forms of print editions will disappear—not overnight—but let’s face it: the modern print industry is still a volume-driven business. Reduce the volume and the profits might very well vanish…

So I not only see the means and opportunity for *all* packaged information to go digital, but I also see plenty of motive. It’ll take a decade or two, of course, but the endgame is already in sight. We just need to look beyond the short-term issues of the day and the limits of the *currently* deployed technology; Kindle and its kin are not the last wordinformation delivery hardware and ePub and its kin kin are hardly the end-all-and be-all of publishing. The storm is just beyond the horizon people, but its coming; the satellite picture shows it clearly.

For example the cookbook. You are right in that we won’t see cook-e-books, but from this it does not follow that we will stick to cook-p-books. What I think will happen is that we get neither but instead cooking apps running in the kitchen communication with my fridge and stove. So I will not get generalized recipes for roast beef from a cookbook but an adapted recipes for the very piece of roast beef I have purchase. Then the cooking app will also control the oven so that it can manage the time and temperature based on feedback from a sensor I stick in the roast beef.

Just because something is being done as books now and don’t make sense as e-books doesn’t mean they have to stay as books at all.