Complex sentence: The stories are interconnected by recurring characters and several loose plot lines (in particular, preparations and execution of a fictitious amphibious invasion code-named "Alligator") but focus on interactions between Americans and a variety of colonial, immigrant and indigenous characters.
Split into simpler sentences: The stories are interconnected by recurring characters and several loose plot lines. The focus of the stories is, however, the interactions between Americans and a variety of colonial, immigrant, and indigenous characters.