This blog gives a good general intro description of how to start out a digital publication. Some people say that the design should be portrait only because magazines are all in a portrait sizes. However, people who would use tablets are very custom to landscape websites and television. So there isn’t a wrong way to set up the design, but having both orientations makes the user use what they prefer. To have both orientations, each one should have its own design. Having one just rotate won’t make it a successful layout. Things will need to be rearranged.
In terms of swiping, it’s usually vertical swiping for pages, horizontal for articles. The other way around has been done and it also works. Visual indicators for end of articles and starts of a new one is a good idea.