No, you are not considered self-employed from the information you provided. The income from the royalties received on the sales of your textbook should be reported on Schedule E, so you would choose the option "Royalty investment income from a natural resource, intellectual property or other investment portfolio" when entering your 1099-MISC.
- Schedule E is used to report passive royalties. Since you are not actively pursuing income from the textbook, this meets the definition of a passive activity.
- Schedule C is used for a business you operated with the primary purpose of profit, and that you are engaged in regularly.
Here are the instructions for reporting How do I enter a 1099-MISC for royalty income?
