I'm not sure what you mean with "run together" versus "separate each page" - do you mean that you want clear, pre-defined page breaks throughout the book?
You can add specific page break in (at least) two ways:
- with the css property "page-break-before: always;" or "page-break-after:always;"
- with the custom html tag <mbp
agebreak>
But use that sparingly - use forced page breaks for example at the start of new chapters, not in the middle of running text. Different devices have different screen sizes, and text size, margins, and line spacing varies too. As a book designer you can't know how much text fits on one screen when a reader reads the book on her device.