That's what Plastic Logic has in mind for its QUE reader, scheduled for launch next year. The QUE boasts a less-reflective screen as well as being lighter and more robust than the competition, Plastic Logic has demonstrated flexible screens too, but reckons that the technology isn't ready for rollable screens just yet.
Unlike Polymer Vision, who went the whole hog with a screen that literally wrapped around a device called the Readius and unrolls when needed. Polymer Vision got to working prototypes before it went titsup, and we got to play with a Readius briefly. The company has since been bought up for its technology.
The Readius - it really worked, just not for long enough to save the company
Despite its (literal and functional) flexibility E Ink's technology is still crippled by its appalling refresh rate, and the fact that it's really hard to extend in to colour.
Does Colour Matter?
Not that colour is such a big issue for some of the more-interesting applications. The ability for an E Ink screen to hold its image without power lends itself to some really innovative applications including Lexar's USB stick that shows available space on an E Ink screen that updates when power is available but displays all the time:
Samsung's Alias mobile phone handsets uses E Ink panels instead of keys, allowing the keyboard to shift between landscape and portrait along with the screens: providing hardware keys with the flexibility of being soft.
Tiny E Ink screens are turning up in all sorts of places, such as Motorola's latest enterprise handset that has one embedded in the battery: an innovation that the designers admit was driven by the incredibly cheap cost of the E Ink screen rather than any functional necessity, nice as that functionality is.
When Rainbows Are Necessary
But it seems everyone is waiting for colour, despite the obvious technical problems. E Ink has a plan to colourise its offering with three layers of microcapsules, combined with filters, but that's not going to happen until 2011 at best, and its hard to imagine the process won't result in dull screens more reminiscent of early LCD rather than something competitive with OLED.
Not that everyone is waiting for colour: earlier this year Fujitsu started selling colour devices with all the advantages of E Ink, though the FLEPia technology comes with its own limitations.
The most obvious of those is price: the FLEPia reader launched earlier this year comes in at around £750 for an eight-inch screen, compared to £450 for iRex's similarly-equipped (but greyscale) version (both devices having Wi-Fi but no cellular connectivity). But the FLEPia's touted 260,000-colour display has another problem: it can take 8 seconds to refresh at that depth.
Electronic ink in colour, for patent people with deep pockets
FLEPia works by having three layers of Cholesteric Liquid Crystal (CLC), which twists in much the same way as modern LCD but remains twisted when the power is removed. FLEPia uses three layers of CLC, tuned to reflect red, blue and green light, with a light-absorbing (black) surface underneath. But twisting all those crystals takes time, so the FLEPia generally only displays 64 colours, with a refresh rate a shade under two seconds. pumping that up to 4,096 puts the refresh rate up to five seconds while anyone wanting to enjoy the whole range of colour available will have to wait for eight seconds for the privilege.
FLEPia technology will, no doubt, improve, but if you're wanting really bright images in colour then the whole concept of layers has to be removed and materials manipulated at a much smaller scale to create colour as vibrant as a butterfly's wing.
The best contender there would seem to be Photonic Ink (P-Ink) as promoted by Toronto-based Opalux. P-Ink involves mucking about with the structure of crystals, tuning them to alter the frequency of reflected light so it appears the colour of choice. P-Ink is impressive stuff, but don't expect it to appear in a Kindle any time soon.
Until then we're just going to have to get used to reading our electronic literature from greyscale screens, or resort to liquid smeared on paper if we really can't do without colour pictures. ®
Time to upgrade
"You'll be wanting BOOK version 9, then." 
@Trygve - I DONT WANT AN E-READER
Why should I have to buy a whole new computer and all the crap that comes with it - why cant my phone, laptop, netbook... have a (bluetooth) Digital Ink screen so I can read with that. It would be light (weight wise) and do all the things an e-reader does - apart from making someone else rich selling me shit I've already got and probably run for days on a rechargeable AAA battery.
I could have a nice black and white one for now, and colour as I see fit - except the people pushing this have a different agenda.
I have a solution
or at least I think I do. One that also neatly circumvents Charles King (above)'s problem of resolution and Matt Bucknall's opacity problem.
Rather than using black and white charged-balls with no backlight, what's to stop them using black and transparent? Actually, black and white balls would probably still work but you'd need a brighter backlight...
The idea would be that you'd have the e-ink screen suspended over an OLED screen. Each OLED pixel would be the same size as the e-ink pixels- they're a lot smaller so it should be easy. OLEDs have been used in flexible displays as well so there's still no limit to how they can be applied.
The e-ink would permanently show a greyscale version of the image, which would be coloured in by the OLEDs. This would still be low-power as OLEDs are low power and could be set up so only the image-covered portion of the screen was consuming any power at all- and with the refresh rate limitations of e-ink you're not talking about needing super-advanced display controllers.
When power was turned off or the OLED reaches the end of its useful life you'd be left with a greyscale image- perfectly satisfactory for a large number of tasks. However, when you wanted the full experience you'd be able to turn on the OLED backimage- giving you glorious colour and the ability to use it in the dark without a torch.
Such a device would be slim, use very little battery power and cost only a bit more than a normal ebook reader (depending on OLED costs...). Black/White-Fluorescent-material balls could make it even lower power as you could pulse the OLEDs rather than keeping them on all the time.
If using black/clear balls you could always put a layer of paper (or another flat white layer) between the OLED and the e-ink so it goes white when OLED power is off. Or use clear and white so it's either white (i.e. virtual "paper") or see-through(i.e. coloured)/grey/black (the colour of a non-powered OLED display).
Alternatively you could use PLEDs or some other type of really skinny light-emitting system as the backimage
If such a device is now released, you heard it here first... and if you heard it here then built it and made money, please get in touch with some royalties or a job as I'm skint and unemployed...