Frank Miller is a legend in comics, when he was the creative mind behind Batman: The Dark Knight Returns, Sin City, and Ronin. But Miller's career can be broken into two parts: pre-9/11 and post-9/11. The latter half includes Batman: The Dark Knight Strikes Again, Holy Terror, and The Dark Knight III: The Master Race.
Luckily, 300 was release in the former half of Miller's career, and while not historically accurate, it gave the world a fun glimpse into the Spartan lifestyle. The downside is the film adaptation gave the world Zack Snyder. 2018 will see the release of a prequel to 300, Xerxes: The Fall of the House of Darius and the Rise of Alexander, from Dark Horse Comics. As the title suggests, it will follow the Persian emperor Xerxes, who raised a massive army to invade Greece in the fifth century B.C. to get revenge for his father's death and become a god. It also suggests the story will see to the rise of Alexander the Great, who destroyed the Persian Empire a few centuries after Xerxes' reign.
Though if Dark Knight III: The Master Race is any indication, Miller might not have much to do with this book.