First let Joe Carter dispel some of the myths. Here are his points:
1. (Almost) nobody will read your book.
2. You won’t find your book at the front table of Borders.
3. Most book marketing today is done by authors, not by publishers.
4. You won’t make much money.
Read his post for an explanation of each point.
Public acknowledgment: Joe Carter, an author himself (who has probably sold more books than me), was kind enough to read and review my dinky book.