Yes I have written a whole ebook and it took me nearly a week but it was a great product when I finished it and I sold some copies as well. I have even written a book on how to take PLR and rewrite it.
Well, I try to sell those products which are less competitive and I take help of Google Adwords keyword tool then I search in Google, if I find that it is less competitive I would create pages on that product, and I would try to rank them in Google mainly.
A Product should be such that it should satisfy all the needs , wants and Desires of the people. A product only becomes salable when its promotion is Targeted towards Niche Audience. The Promotion of the product should contains Good Campaign, Effective Banner ads.
I would to like to suggest you to build the strategy in order to promote your product. Initially, you can start using SEO techniques like Email Marketing, Social media, Blogs posting, Forums posting, Article submission, Directory submission etc. are all part of online marketing. Later, once you start receiving traffic for your product, Displaying ads, use of Adwords and Adsense can be another option to promote your product.
well, I always believe email marketing is an effective promotion methods. To learn how to do email marketing, you can refer to this free eBook: http://emailmarketing.comm100.com/email-marketing-ebook/