Among the great typographers of the more distant past were Francesco Griffo in the fifteenth century (designer of Bembo and italics), Claude Garamond in the sixteenth, and John Baskerville in the eighteenth. The faces such as they created are called Old Face (or Humanist).

Around 1800 hideous typefaces were introduced, collectively called New Face (or Rational): these are what make nineteenth-century books (and many twentieth-century American and French ones) so hard on the eyes. They were intended to be designed with geometric exactness instead of mirroring the intuitive beauty of handwriting.

New Face was largely abandoned in many countries in the early 1900s, with the work of Stanley Morison (1889-1967, designer of Times New Roman), Edward Johnston (1872-1944 designer of Imprint and the London Underground's Railway Type), Eric Gill (1882-1940, designer of Perpetua and Gill Sans), and later Max Miedinger (1910-1980, designer of Helvetica, which has the distinction of being one of the few truly beautiful sans-serif faces), and Hermann Zapf (b. 1918, designer of Palatino, Optima, and those dingbats). Some of these are wholly new designs but many are a return to the classical beauty of Old Face.

Sans-serif is usually considered less easily readable than serifed, and appears somehow less trustworthy, but the only scientific study that supported this was...ahem... by Sir Cyril Burt. That's less easily readable in print: a computer screen doesn't have the resolution to be able to show serifs to advantage.

Essential, very informative site on all aspects of typography, with biographies, samples, sales etc etc:

The old artists of the classical school were never egotists. Egotism has been and remains responsible for many defects of modern typography.

Talbot Baines Reed

Typography may be defined as the craft of rightly disposing printing material in accordance with specific purpose; of so arranging the letters, distributing the space and controlling the type as to aid to the maximum the reader's comprehension of the text. . . . Typography is the efficient means to an essentially utilitarian and only accidentally æsthetic end, for the enjoyment of patterns is rarely the readers's chief aim. Therefore, any disposition of printing material which, whatever the intention, has the effect of coming between author and reader is wrong.

Stanley Morison