I've been reading books on my phone ever since I had ye olde Siemens S65. I've switched to touchscreen phones the instant they became available exactly because I could read books on them more comfortably.
LCD screens work just fine, especially the newer "retina" displays. The only time you might have a problem reading them is in direct sunlight on a cloudless day with the sun directly above.
As a bonus point, LCDs are much more readable in pure darkness than eInks.