In his book The Elements of Typographic Style, Robert Bringhurst sets forth what he considers to the be the ideal for setting text. He states:
- 45 to 75 characters line length (measure); specifically 66 including spaces; Single Column
- 40 to 50 characters; multi-column
- 85 to 90 characters; discontinuous text; generous leading
- 40 characters (minimum); justified
- 12 to 15 characters; marginal notes; English
He also discusses the ideal page to great detail on pp. 171–176.
I'm hoping to find other authors who've written down their ideals. What have you found as you've read? Would you share your findings? Even just the books and page numbers would be helpful.