What has the author John Shipman written?

It seems you're asking about an author named John Shipman. However, there is no widely known author by that name. It's possible:

* You might have misremembered the name. Do you remember any other details about the author, like their genre, or any specific titles?

* The author might be relatively unknown. There could be many authors with this name who haven't achieved widespread recognition.

* It could be a pseudonym. The author might use a different name for their work.

If you can provide more information, I can try to help you find the author you're looking for.