In the introduction of Typefaces for Books, James Sutton and Alan Bartram argue:

While display faces can be extrovert, colourful and rich in character, book faces must be transparent, allowing the reader to hear the author’s voice without distortion or interference.

It is in answering this little question of the author’s voice that the book typographer’s task lies. He must invent an action, a tone, and decide on the volume: should he whisper or shout or sing? whatever he decides he must keep in mind that he is making a window through which the reader can see the view as clearly as possible and be quite unconscious of the proportions of the glazing bars.

In Shaping Text, Jan Middendorp writes:

A good jazz musician will master different styles and genres in order to feel in control in various formations or in jam sessions. A professional graphic designer, too, will have to improvise and find ways of communicating all kinds of contents in all kinds of circumstances.

In Design Elements: Typography Fundamentals, Cullen writes:

Type for the web, as well as digital devices and gestural interfaces, meet challenges because conditions vary, unlike fixed mediums such as print. Multiple browsers, platforms, and screen sizes present type differently. Typefaces suited to one might not suit another. Expect the unexpected in digital realms. Be flexible and responsive. Digital formats know no bounds. Unlimited virtual space offers potential unseen in other areas.

In the introduction of Designing Type, author Karen Cheng writes:

Type is the visual manifestation of language. It is instrumental in turning characters into words, and words into messages. In music, the quality of an individual singer can completely change the experience of a composition. In communication, type is the visual equivalent of an audible voice – a tangible link between writer and reader.

In the preface of Letters of Credit, Tracy argues:

The use of typography is a matter of taste as well as sense; and the fact that typographic letter forms are an inexhaustible source of interest and pleasure is a thing to be grateful for.

His view on type as human creation:

Not long ago it was taken for granted that the people most interested in type faces were those who used them, or actually created them: typographers, publishers, printers and, of course, type designers themselves. But in recent years another set of people, quite different from those with direct involvement, have developed an interest in printing types. They are the academics—the mathematicians, computer scientists, psychologists, even philosophers—who have found it worth their time to theorise about the nature of letter forms as human creation, one of the things that other animals do not have.

He concludes:

Typography may be no more than ‘a minor technicality of civilised life’, as Stanley Morison remarked, but it deserves the best we can give it.

In White, Hara writes:

Despite the cultural boundary between East and West, and the technological gap dividing those civilizations, the sense of beauty attached to typeface has been cultivated through the simple act of placing characters on paper. In this regard, Guttenburg’s cast type and Chinese woodcut printing share a common feature. Letters became independent objects through the sheer fact of being printed in black on white paper.

Prof. Phil:

Good typesetting is a craft and skill set that you will spend your whole career trying to master.

There is very little design where type does not make up over 50 percent of the graphic communication. So learn to use it like you learned to walk or ride a bike, as you will always need to be able to control it. Good type makes or breaks a job.

Six simple typographic rules I use as basic guidelines for setting type.

1. Read the content first.
2. Start with the body text.
3. Choose no more than two typefaces.
4. Apply grids and modular scales that honor content.
5. Use hanging punctuation to not disrupt the text alignment.
6. Allow generous white space.

Tschichold:

Good lettering demands three things: — (1) Good letters. A beautiful letter form must be selected which is appropriate to the purpose it is to serve and to the lettering technique to be used. — (2) Good design in all details. This calls for well balanced and sensitive letter spacing and word spacing which takes the letter spacing into account. — (3) A good layout. An harmonious and logical arrangement of lines is essential.

The intro of Jan Tschichold’s Treasury of Alphabets and Lettering has useful guides on letter spacing of capitals and lowercases.

Frutiger on Méridien (1957):

The most important thing about Méridien for me was its even rhythm. However, the overall impression wasn’t supposed to be rigid, but lively and organic and therefore reader-friendly.

Frutiger on Univers (1957):

Univers, however, would have been unthinkable without a constant width skeleton, it was only the concept of a systematic widths that made the many varieties possible.

Frutiger on Egyptienne (1958):

[Egyptienne’s] a useful text face, as the baseline is very good, distinctive and stable under any exposure.

Frutiger on Frutiger (1976):

My masterpiece is Univers, but my favourite typeface—if I’m being honest—is the original Frutiger.

Frutiger on Centennial (1986):

Centennial is one of my most professional typefaces; it was created on the back of 25 years’ experience of type design, with absolute logic—and feeling, naturally.

Frutiger on Avenir (1988):

Univers was a striking idea, as was Frutiger, but in Avenir there’s a harmony that’s much more subtle than in the others…My personality is stamped upon it.