Over the years I’ve scanned and OCR’ed many printed books into electronic form for Gutenberg Australia—most of the Edgar Wallace collection there is my work, for instance—and during that time it’s become clear that not all typos are equal. After awhile, in fact, it became possible for me to divide typos into categories, as follows: Category 1: Typos due to English orthography Some letter sequences in English serif text happen to resemble others. The sequence ‘of her’, for instance, looks very much like ‘other’, and ‘thing’ looks very much like ‘tiling’. Every second or third book I scanned had these mistakes in it...