Like some other commenters already mentioned, repurposing content is a viable tactic. Still, as with any product you are trying to sell, it can feel like the proverbial drop in the ocean.

To actually sell your eBook you will need considerable amounts of visibility. So it's really the whole package these days: Social media, blogging, author page, paid ads - the whole shebang.

I miss the good old times where books made up almost all the available media out there.