[kacir]

Originally Posted by derangedhermit

To be specific, I counted. <50 characters per line is clearly better left justified, and >60 characters per line, I prefer full justified.

Right.
Text with too short lines is difficult to read, because the eye has to jump often and full justification produces very weird articacts.
Text with too long lines can be very uncomfortable. Your eye won't be able to find the next line when you finish previous one. Just open a text on a full length of a 24 inch monitor and you will clearly see what I am talking about.

In printed books, [the average of] 56 characters on line is considered to be THE ideal number of characters for the best readability. Most sources that do study the optimal length of the line of text say that the value should be somewhere between 50 and 75 characters. Just grab a well formatted paper book and count.
When the text is this long, a fully justified text can look much neater and the variation in inter-word space width is not distracting. For this to work really well, you need hyphenation (that surprisingly high number of e-ink readers do not support at all!) and a well made program to do the layout *and* it still has to be looked at and hand-tweaked by a skilled typographer.

For shorter line length and missing hyphenation and ridiculously wide margins and font size that can't be finely tuned and non-existent typographic tuning of spaces in software(such as inDesign or LaTeX have) - which is, sady, the description that fits many of modern e-ink devices - the left justification is better.


The best solution would be to let the user choose. I can't understand why there is no such choice for most of the reading devices "out there". Even such well configurable device as PocketBook, or great third-party programs installable on some readers, such as Coolreader, this has to be set by configuring it in a text configuration file or CSS override file.