With a working title of ‘Beginnings’ (original or what?) the prequel to Electra is currently sitting at 8500 words. I’m aiming for a total of about 15-20000 words. to put that into context, Electra was 88000, and in a paperback edition runs to around 300 pages, so Beginnings will be about a bit less than a quarter of that. It’s intended to be a teaser for the series and an explanation of the origins of the Seven Sisters rather than a novel in its own right.
And just for the record, the fact that there are seven sisters doesn’t mean that there will be seven books in the series. I’m not sure yet how many there will be but some of the books will focus on more than one sister.