We are all used to searching, but browsing in the stacks can be a very fruitful approach to finding material on your topic. If you understand how the books are arranged on the shelves, you will have a better chance of finding what you're looking for.
Plus, anytime you go to the stacks to get a book you found online, be sure to look around it at what is nearby. You are likely to find something else!
The books are placed on the shelves according to a system called the LC (Library of Congress) Classification System. The "call number" on the spine of each book is its address for where it lives on the shelves as well as an indication of the major topic of the book.
You find the call number in the library catalog:
The label on the book will look like this. Read it line by line.
To explore an outline of all of the call numbers, start here.