Lots of authors do updates via Twitter and Facebook as well, or post update information on other blog sites like Tumblr. Your best bet is to check the author profile, and see if they list any sites where they post updates.
If the author posts updates in our Promote a Story thread, you can follow that author's topic, and get email notifications that way.
Aside from all that, all you can do is do what CL recommends, and ask the author.