Since it's taking time to get my Amazon pages consolidated and I'm still working through upload issues, the only promotion I've been doing is twitter. I'm in a pattern now of about 3 tweets a day. Morning/Afternoon/Evening. It takes me less than a minute to do. So the question would be does it work and is it worth doing.
My short term objective is to keep from falling into Amazon book ranking oblivion, until I have things in place to do my other promotions. The only place I'm driving sales is on twitter. My results: I've kept my amazon rank between 50K-70K since my release day, which will make it easier to break into the top 100 list once the promotions kick in. I've had enough sales to be profitable on the project first month out( I allocate the cost of releasing a book over 12 months to keep it in manageable goal range). And today, my prime member book borrowing has started to pick up.
Whatever the results, tweeting doesn't cost anything. I can say it's helped me to maintain my strategy goals.