don't listen to ebookie.
there is no reader for the symbian platform (that your n95 uses) that can read the MICROSOFT .lit format.
there is mobipocket and ereader available for symbian. both are widely available, personally i prefer mobipocket since it lets me read HTML, TXT as well as it's own mobi format.
as far as eyesight is concerned, don't sweat it. all readers allow for font-resizing, my sonyericsson p1i has about the same screen size as your n95 does, and i can read comfortably with 15 lines of text per page.
i set the background to black, text-color to light gray, and it's perfect. also, your phone might allow you to dim your screen so if you're in a completely dark room the brightness won't hurt your eyes.