The Dewey Decimal Classification is a way of organizing books by subject. It assigns each book a number (called a Dewey Decimal Number) based on what it is about. For example, if you want to find a book about animals, you would look for books with the Dewey Decimal Number 590. This number is made up of two numbers: 5 stands for animals and 90 stands for general and miscellaneous topics about animals. If you want to find a book about dogs, you would look for books with the Dewey Decimal Number 599.99. That number is made up of the first two numbers from the animal section (5 and 90) and the last two numbers mean books about dogs. The Dewey Decimal Classification makes it easy to find books about what you are interested in.