What has the author John Gregory written?

There are several authors named John Gregory. To answer your question accurately, please provide more context, such as:

* Full name: Is it John Gregory, John S. Gregory, John D. Gregory, etc.?

* Genre: What type of writing are you interested in (fiction, non-fiction, academic, etc.)?

* Era/Time period: Are you looking for books written recently, or from a specific era?

Once you provide more information, I can help you find the author's works.