help with typography

[Freehand 5.5]

I'd like to expand on Freehand's first line a little bit. There are two related qualities a font has: readability and legibility.

Ah, thanks for telling more precisely. In German there is only one word (Lesbarkeit) for reading and consulting text. So I didn't know the word legibility - but I meant it for sure.

I'm going to politely disagree with Freehand concerning the number of typefaces on a document. I wouldn't use more than three fonts in a single map. One for large labels, one for small ones, and maybe a third for cartouches. You can get some additional variety by adjusting size and color, and by using the italics variant. I prefer to let the symbols indicate what a particular feature is rather than using a different font.

Perhaps you misunderstood, what I said, because the word typeface and font isn't the same. A font (-family) may consist of many typefaces (book, bold etc.).
So if you label settlements you could use many different typefaces (e.g. book, medium, bold) of one font to indicate size without using more than one font.
Or you label all water-things with italic typefaces of the same font.
So speaking of typefaces I think there is definitely the possibility of more than three. If it comes to fonts, you are right, but that wasn't what I said.

But I think, in creative work (especially typography for stylish and unreal fantasy maps) there is no such thing as a quick recipe of bulletproof design. Talking about the maximum of fonts, typefaces, colors, shapes or anything will always go beyond the limit of some special definitions of a project. Every advice could only be a friendly hint.
Good example for breaking the rules was a nice map I saw some days ago, where multiple things were set in another font, chosen in the style of the things they represent. From a typography scholar's point of view a no-go, but how cool it worked out in that special case! Unfortunately i can't find the link, but the map was called continent of Aarklash.