I liken writing to the law of averages, the average person wants to write a book ( some say the number is as high as 90%) still the law of averages says that only 20% will write a book and of these only 5% or less will publish it.
The same things go with self-publishing, but as Al pointed out, with good marketing, you will have a better chance to sell.
So I asked a few people what would you say would sell better?
A published book in fiction or non-fiction?
Going with self-publishing, the law of averages state the bestsellers (whatever each group defines as such) are how to or non-fiction books.
I suspect that this would be the same if you were to traditionally publish.
Bearing this in mind, what would you add to the law of average in publishing non-fiction?