So many clients come to me as a book or marketing coach telling me how they spent and wasted a lot of money and time following different well-known gurus in the book and publicity fields.
Yes, you know your subject. You also need to think about entertaining your audience, and making your book or other writing easy to read.
It's a good idea to use TextPad because all opt-in ezine publishers want your articles without any formatting. Also, for any email exchange, you need to put your article in the body of the email, not an attachment.