In the history of calligraphy, many books have been published on the subject of letterforms, but until Uncommon Numbers: A Source Book for Artists was released by PenUltimates in 1996, there were no books in print dedicated to the subject of calligraphic numerals. An instructional book, The Uncommon Numbers Manual: A Guide to Harmonizing Beautiful Numbers and Letters, followed in 1999; and the trilogy was completed in February, 2010 with the publication of Uncommon Numbers II: A Source Book for Calligraphers and Graphic Artists.

The first and third books are anthologies showcasing the work of internationally known master calligraphers from around the world, and the middle volume is a manual offering the kind of in-depth analysis and step-by-step instruction traditionally reserved for letterforms. The Uncommon Numbers Trilogy: Source Books for Calligraphers and Graphic Artists is now available as a three-volume boxed set. These books remain the only titles in print dedicated to this subject and are considered by many to be essential to the libraries of all serious calligraphers.