At the end of May I posted a long analysis of my experience with the free Kindle promotion of "On Angel Mountain" -- the first book of the Angel Mountain Saga. You can find it
Most authors and publishers are very reticent about sales figures, but I don't mind sharing this! Bearing in mind that before the free promotion, sales of my titles were bumping along at a rate of two or three a week, there was an immediate and spectacular increase in sales in the days following the promotion. There were 239 sales of "On Angel Mountain" in that first week, and also a big increase in sales of the other titles as well, with total sales for the five titles reaching 306. Not exactly stratospheric, but some people out there must have liked the free book enough to buy some of the others, and some readers must have told other readers about the books. A few hundred quid is not a fortune, but it's not to be sniffed at if you are a "mid-list" author!