The Sharp Memory LCD screen is opaque, unlike most other LCDs, so can't work with a backlight. It could work with a front/edge light but the results are not what you'd hope for.
As far as I can tell it works if you've got basically any amount of light at all, though it might involve tipping the display around until you catch a reflection at the right angle. It's more E-paper-y in looks than LCD-y, though the reflectivity is fairly unique.