TrueType fonts are handled incorrectly
Wherever any GUI elements are being scaled, for example books, or all parts of the GUI if you have scaling enabled in settings.cfg, text will be rendered at what the game considers to be normal size, then scaled up to match your settings, meaning it can't take advantage of the higher resolution to provide better clarity and sharper text. Using Morrowind's original bitmap font, this would not make any difference, but when you use a TrueType/OpenType font, you'd expect to be able to take full advantage of the added resolution. This also applies to the console, which is rendered using a TrueType font by default. The following screenshots were taken at 4K resolution with scaling factor 2.0 set.
(RM-3288 from redmine: created on 2016-04-01 by Isak L, , duplicates #3685 (closed))