@Pinecone - I believe the OP is talking about the "metadata jacket" functionality of calibre, where it adds an extra page to the inside of the book with a summary of certain data about the book.
@MrKayMrKay - I don't use metadata jackets myself but from what I understand of the functionality you are out of luck. The metadata jacket functionality is only available by either doing a conversion (or by using the Modify ePub plugin). Both will result in an updated format in the library, leaving it up to you to manually revert things. It is a slightly odd request to be honest, unless you were using multiple devices and had some users who liked jackets and others who didn't. I think you shall have to decide on one or the other
