Investors & landlords

It depends.  

Schedule E is used to report passive royalties.  If you are not actively pursuing income from the book, this meets the definition of a passive activity. If you received a 1099-MISC, you would choose the first option when entering the form  "Royalty investment income from a natural resource, intellectual property or other investment portfolio."  

If you did not receive a 1099-MISC, enter the information by navigating to Federal > Wages & Income > Rentals, Royalties, and Farm > Rental Properties and Royalties (Sch E). There, enter your royalty income as an "other" royalty.

 Schedule C is used for a business you operated with the primary purpose of profit, and that you are engaged in regularly. If that describes your work as an author, the royalties will be reported as gross income in the self-employment section of TurboTax. To enter this, navigate to Federal > Wages & Income > Self-employment income and expenses.
 

Here are the instructions for reporting  How do I enter a 1099-MISC for royalty income?