How to return to original writer document formatting?

Writer has started opening documents with first page far to the left of screen and subsequent pages like two columns. How do I stop this from happening?
The document still prints the pages separate. I think it is just the on screen formatting that is messed up.

You have inadvertently turned on Book preview. Down in the bottom right corner next to the zoom slider are three page icons, click the single one. Cheers, Al