Are the royalties I received for writing a book subject to self-employment taxes ?

The Royalty checks for writing a book is considered income subject to self-employment tax if the recipient can be considered to be regularly engaged in that business or profession and will report this activity on a Schedule C.
The Royalty checks for writing a book is not considered income subject to self-employment tax if the recipient writes only one book as a sideline and will report this activity on a Schedule E