When measuring a book, the most appropriate unit of measurement is typically the mass. The mass of a book can be measured using units such as grams (g) or kilograms (kg). It refers to the amount of matter contained in the book and is independent of gravity.
On the other hand, atomic weight or mass number is not applicable to a book. These terms are used in the context of atoms and elements. Atomic weight is the average weight of an element's atoms, taking into account the different isotopes and their relative abundances. Mass number refers to the sum of protons and neutrons in the nucleus of an atom.
While a book is composed of atoms and has mass associated with its constituent particles, the concepts of atomic weight or mass number are not directly applicable to a macroscopic object like a book.