Every bookstore must have bookshelves to display books. Bookshelves are arranged in rows to enable visitors browse the books based on the categories and titles that they are looking for. When a bookstore is crowded by book lovers, the space between the bookshelves have to be wide enough for at least two people moving in opposite direction without colliding each other and without hitting the books. Therefore, there has to be a standard width to allow book lovers to walk around inside the bookstore. From my personal experience 1 meter is a reasonable distance for home based bookstore with only small room whereas 2 meters are recommended for large bookstore. Bookshelves can be manufactured from wood, metal, or plastic. Metal bookshelves do not need a lot of space when installed leaving enough space for people to walk around.
As an owner of a home based bookstore, I give one meter space between the bookshelves to provide an area for book lovers to stand between them and read the information at the front and back covers of each book. Actually 1 meter is too narrow for adults but they are adequate for home based bookstore because the bookshelves are short. In addition, most of the visitors in my bookstore during the busy time (between 9 a.m. - 1.30 p.m. are elementary school children. How many bookshelves do I need in my bookstore?
In countries where the average body size is bigger than Asia, the standard space will be 1.5 meters for home based bookstore. I cannot give accurate assessment to this because I have never visited any foreign countries. So, 2 meters are good because it provides enough room for 2 people facing the respective bookshelves while one is walking a long the aisle. In other words, the space between the bookshelves is enough to accommodate three people standing in different poses - 2 facing the books while another is walking. That's my personal recommendation. If your store is not a bookstore, you will need to see the design of the shelves and their standard dimensions from Data Architect, a very good book - written by Ernst Neufert. In this book, Neufert recommend 120 cm as the standard space
Also read: How to manage a bookstore