Here's link to abstract and full pdf for free:
http://www.jemr.org/online/5/3/5Interesting study but by no means conclusive and has a few flas as they only measured 6 female participants reading 300 words at a time on each device.(10 inch ipad, two sony e-ink devices of 6 inch variety)
Number and sex of participants might not be that crucial here but 300 words at a time seems very low amount.
Anecdotally, I can read just fine and quickly on a most glossiest of LCDs for a few minutes.
If I have to read for an hour or longer give me e-ink screen any time.