As a novelist, I have always favored something novel. I strive to be original in both my style and my subject matter. As a historical novelist, I am drawn to the "untold stories" of history. I like to "discover" historical events that have been forgotten or neglected, and bring to life historical figures who have been locked away in dry and dusty history books but not handled in literature.
This may explain why my success to date is so modest.
Readers much perfer to read about someone they "know" than someone they've never heard about. It's the natural tendency of all people to be more interested in gossip about their neighbors than in strangers. If you don't "know" someone, why should you care about them? In the same way, an audience prefers a familiar tune to a new one. Even if we don't particularly like a melody, we'll still find ourselves tapping our feet or nodding our head in time to the tune; we'll hum or whistle or sing along. But if we've never heard a song before, we can't do any of that and so it's more likely to be ignored or switched off altogether as mere noise. Performing artists understand the need to mix new songs in among older songs to get their audience to listen until the new becomes familiar.
With books the interest is more cerebral than instinctive. Just as we go to see a new production of Shakespeare's Hamlet because we want to see how the director and actors interpret the familiar plot and dialogue, we read books about familiar historical events and people in order to she how the author has portrayed them. Thus reviewers often compare authors/books about similar subject matter. "This book makes character x much weaker than author y did in his book z...."
The result, as publishers well know, is that readers are more likely to buy the 101,000th book about Anne Boleyn than the first book about - say - Anne of Bohemia. The more famous the historical person, the more successful a book will be. Richard the Lionheart trumps Ethelred the Unready every time. It also explains why readers perfer to read about their cultural heretage: English history is much more popular to English-speaking readers all across the world than Chinese or Ethiopian history.
From the point of view of novelty and "discovering" the "untold stories" of history, Ethiopia has much more to offer than England, but since I want people to read what I write, so I'm not going to go there. Unfortunately, I'm bored to death by Anne Boleyn and even Richard III at this point so I'm not able to write a single word about them. Instead, I float on the less familiar (but hopefully a little familiar) fringes of Western European history, with my up-coming biographical novels of Balian d'Ibelin and, later, Edward the Black Prince.