[ProDigit]

I have both the Jetbook, and the jetbook mini,
The mini has somewhat an upgraded screen, under certain light angles, the text appears to have a higher contrast; unlike the Jetbook where the angle of the source of light makes little difference in contrast ratio.
The mini's contrast ratio is the same as the jetbook at worst, and better at best.

In either condition, a 0.5 W white LED spot, or a 2-3 watt LED nightstand lamp is good enough. that compares to a ~5W incandescent spot, or a 30-40w incandescent night stand lamp. You could also comfortably read outside under light conditions when the sun just went down.

There are instances where you will be able to read a book under candle light (in a dark room). This is too dark for the jetbook (which has presumably the same screen as the aluratek.

But chances are very small you will find yourself stuck to these conditions. Under any other circumstance, you will have sufficient light to read.

Your issues however will be more the screen resolution, as it has a 640x480 pixel screen, which is barely enough for text files (and if you're lucky, and the device supports image scaling, it would work for epub too).
But pdf in full view is a no on this devices, and honestly, to me, these devices are only good as text readers. So if you don't mind reading pdf's in reflow, or reading regular text files, this one is a nice device.
However, I'm not too fond of the tft screens. they get upto 24 or 80 hours battery life, while that is nothing compared to e-ink which has battery life between 700 and 1400 hours (~7000 page turns), meaning you could be reading several weeks on one battery charge on e-ink, while on tft you'd be needing to charge the battery every 2-3 days.

Compared the Ectaco Jetbook mini (TFT) to the Astak Ez Reader Pro (e-ink) in reading contrast, and I'd have to say the TFT screens give out complete blacks, but the whites are light grey.
E-ink's whites are pretty white, but the blacks are more darkish grey.

e-ink is better readable in darker environments than tft,. TFT is better readable in sunny outside light, than e-ink (as sunlight reflecting of the white e-ink hurts the eyes).

Either one has benefits over the other, but I prefer e-ink's mobility (battery life) over tft!

You could take it to a transatlantic flight, miss a flight,stay a few days in a hotel until your next flight, without having to worry about charging it.