subtitle of the books

Hi!

In the update I am working on, I’m hoping to make it easier for developers to add their own custom fields. Subtitle has such a specific use case (and it’s particularly front-end/theme territory) that I think it might be best to be handled this way. I am adding some new taxonomies, but I don’t want to add so many toggleable options that the options page is just overwhelming and I feel like this feature would be left off in most circumstances.

When I have the developer template tags/hooks built in and documented, I will post back here with a link on how to do it.