There is something extra interesting about ancient cultures. They just seem so far removed from your everyday life, and that makes for some quite interesting historical fiction. Most of that is centred around the ancient Romans and Greeks, which makes sense. They are the ones, along with the Egyptians, we learn about in school, and also they were the ones who liked to write things down. That makes life a lot easier for historians, and by extension authors of historical fiction. Either way, it's amazing that authors are able to write fully fleshed out worlds and characters for people who lived a couple of millennia ago.