The Art Of Typewriting, by Marvin and Ruth Sackner, is the first truly comprehensive survey of typewriter art. It has a foreword by Steven Heller (author of Illustration, amongst many other books on graphic design), and begins with an excellent history of typewriter art. It's an especially well-designed book: each copy has a different cover design - mine is Ruth Wolf-Rehfeldt's Introverse, also reproduced on page 162 - and it includes a bookmark that resembles a typewriter ribbon.
A taxonomy of typewritten artworks, comprising more than 200 full-page plates (mainly, though not entirely, from the Sackners' archive), is followed by illustrated biographies of key typewriter artists. The book contains numerous examples of typewritten concrete poems and 'poesia visiva' (visual poetry), though it doesn't differentiate between these two overlapping styles; instead, the authors coin the umbrella term "typed artpoe" (a combination of 'art' and 'poetry').
Barrie Tullett's similar Typewriter Art: A Modern Anthology was published only last year, though The Art Of Typewriting is far superior: it's twice as long, and it includes a bibliography. Tullett makes only passing references to pioneers of typewriter art such as Julius Nelson, Paul Smith, and Montserrat Alberich (and omits George Flanagan), though The Art Of Typewriting includes multiple illustrations of their works. The most impressive is Alberich's incredible typewritten picture of a cathedral, an image supplied by the Museu d'Historia de Barcelona.