How does one close books that you don't want open anymore in the IPhone App?
Open something else.
On my iPhone they all stay open. Currently have 5 books on the ribbon visible when you tap at the bottom of the page (when reading).
Yeah, how to close the books?
OH....the book is technically closed. But how to remove it from the ribbon is a good question. I'm not sure about this one.
You can really only have one book open at a time, but the app keeps track of the last 25 viewed books. You can think of the list as recently viewed books instead of open books.