Nowadays, quite a few ebooks are being sold on the topic of niche marketing. Most of them are written by people that haven't really "been there and done that" themselves. They just see an unfolding trend toward niche marketing and decide it's a good bandwagon to jump on. In contrast, I've been selling online to niche markets for years (and doing quite well!). I was dealing in niche markets before niche markets were 'cool'.