the metric system
You measure it.
Instruments such as calipers, rulers, and tape measures can be used to measure the width of a book. These instruments provide an accurate measurement of the book's width in either inches or centimeters.
With a ruler..... hahaha
Height by width and a ruler. :)
Millimetres
You would typically use inches to measure a paperback book. You can measure the length, width, and thickness of the book in inches to determine its size.
A centimetre should suffice.
The width of a book can vary significantly depending on its type and size. For example, a standard paperback novel typically has a width of about 1.5 to 3 centimeters, while larger hardcover books might range from 3 to 5 centimeters or more. When considering specific books, it's best to measure them directly for precise dimensions.
A centimetre, although you could use a millimetre for greater accuracy.
Inches or centimetres are fine for a book's dimensions. Measure the width, height and depth to determine the volume. If you are talking about the length of the book's narrative, word count is probably the most accurate.
You would typically use centimeters (cm) or millimeters (mm) to measure the width of a book. These units provide a more precise measurement for smaller objects like books.
Base x Height x Width = Volume of any rectangular prism.