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.
meeters?
Time
a millimeter
Millimetre.
The meter.
Centimeters
A kilometre.
Cm .
meeters?
Centimeters
Time
a millimeter
Millimetre.
You could measure the length of a lunchroom in feet or meters, depending on which unit of measurement you prefer to use.
Milligrams
the metric system
Kilometres