Psyringe: I prefer ebooks. Otherwise, paperbacks, since they are cheaper, and easier to handle. They may not be as durable as hardcovers, but I tend to treat my books well, and never had a problem with any of my paperbacks.
hedwards: Indeed, ebooks are clearly the superior book. Both paperback and hardcover tend to be excessively difficult to read and terrible ergonomically.
Probably the only time I've found them to be worthwhile since the invention of ebooks is for some reference books where I need to quickly flip back and forth between pages. In that case, the hard cover is definitely superior as paper backs tend to be more difficult to keep open without holding them.
But really, dead tree editions are horrible and should be discontinued as soon as possible for the betterment of humanity.
I say MORE dead tree editions, I want a library filled with the skins of their kindred filling the walls from floor to ceiling! Seriously though, as much I love the betterment of technology for creating a cleaner society to our world, books are one thing I think should never be gotten rid of. If the problem is the use of trees, find alternate means of paper, or even recycle books that are damaged to the point they would be thrown out.
Also, there is the unlikely but still possible scenario that they did this then some technological "hiccup" occurs and all those books would be lost. That's really something I don't think humanity can afford to happen. I know this is an unlikely case but it's always best to plan for the worst, hope for the best.
I do own an e-reader, and I do enjoy the lack of weight provided by loading books ON to said device, but personally to me books are history and something truly special. Now a reasonable compromise I think, would be to offer considerable discounts to eBook version of titles and say offer a printed version made available to those interested at an additional cost to have one fabricated.
To me there are far more other things the world needs to find alternatives to rather than ceasing book productions. Such as, alternative fuels, alternative power sources, getting the climate shift issues under control, etc... But, most of this is just my opinion, and that's my 2 cents... :)