Here's why:
* Copyright protects original works of authorship, including literary, dramatic, musical, and certain other intellectual works. Books fall squarely under this category.
* Patents protect inventions, which are new and useful processes, machines, manufactures, or compositions of matter. A book, while original, is not an invention.
Key differences:
* Copyright is automatic upon creation, while a patent requires application and approval.
* Copyright protects the expression of an idea, while a patent protects the idea itself.
* Copyright lasts for the life of the author plus 70 years, while patent protection varies by type.
In short: If you've written a book, you have copyright protection automatically. You don't need to apply for it, but you can register your copyright with the United States Copyright Office for additional legal benefits.