How Much Should Authors Share about Their Books in Advance?

Some writers choose to post long synopses for their novels on their websites before the official cover copy is even written. Some post synopses of their unsold novels. Others are more coy and don't even set up websites or Twitter accounts until a few months before a book's publication.

Where do I stand on the subject of sharing info about a pre-published book?

I'm leaning more on the secretive side. Anything I've revealed about the plot of In the Shadow of Blackbirds primarily comes from the sh...