Wiktionary
n. Any of several stylized handwriting scripts used during medieval times. It was intended for legibility and often used in transcribing official documents (prior to the development of printing and similar technologies.)
Wikipedia
A book hand was any of several stylized handwriting scripts used during ancient and medieval times. It was intended for legibility and often used in transcribing official documents (prior to the development of printing and similar technologies).
In palaeography and calligraphy the term hand is still used to refer to a named style of writing, such as the chancery hand.
Usage examples of "book hand".
The ritual was an odd one, from the most ancient of the Wenshar grimoires, its faded instructions jotted in a curious book hand characteristic of the court of that accursed matriarchy which lay open to several interpretations.