Reading on a backlit screen is well known to tire your eyes very quickly, due to the low resolution and (afaik) because the eyes' Rhodopsin depletes faster while staring into a light source.
I have heard people arguing that we spend half our days in front of a computer-screen anyways, but that is a different kind of usage. During computer use the eye is mostly scanning and rarely reading chunks of text longer than a page at once. Book reading is a different story, as anyone who has tried to do that on a backlit screen can confirm.
Consequently this argument about (Book-)typography misses the point for me. If you want a good reading experience then get an e-ink device or stick with paper. Even the best font can only marginally reduce the inherent problems with staring a backlit screen for extended periods of time...