Under those weather conditions you won't be reading, and not just because of the e-ink technology.
The lithium-ion rechargeable battery won't operate correctly at those temperatures. They tend to prefer things be 4C or better.
The e-ink panel actually has a lower range since it is rated down to 0C.
The Sony Librie can have the Energizer e2 Lithium batteries (
http://www.energizer.com/products/lithium/) installed and they are rated to -40C, but that only buys you 4C since even the Librie's panel isn't rated below 0C.
Last winter I used the Energizer's to give better cold weather performance than ordinary AAA's (noticeably better I might add) and kept my Librie in my Eddie Bauer outer jacket's large interior pocket.
If the heater was out on the bus the display could get sluggish but no permanent harm came to it (but we never got much below 0C.)
I know this thread is about Winter, but Summer is an issue as well. And for similar reasons: lithium-ion battery.
If you charge your lithium-ion battery at 40C, it permanently reduces the charge capacity of the battery. Make sure you take your iLiad/Sony some place cool (closer to 25C) to charge it.
For those still using Librie's, I was near the equator for several weeks last year. The Energizer batteries also perform better there during Spring/Summer as well. If you don't flip pages quickly enough in 40C heat the ghosting on the e-ink panel gets much more noticable.