I’ve been thinking lately about the trouble that comes when your players end up knowing more about your campaign setting than you do. While there are thankfully few Eberron books, we Eberron DMs still have the trouble that our players may very well have read the Eberron Campaign Setting and Keith Baker’s Dragonshards on the official website, and may thus know just as much as we do about the setting. That means the players will find themselves knowing the secrets of our campaign setting - Kaius III’s secret, the existence of working creation forges, and all manner of information on creatures who should be entirely unknown to the player characters.
Fortunately, there’s a simple way to solve this. Change your Eberron. It’s your campaign after all, and there’s nothing to stop you from making sweeping changes to the world as written, provided that you consider the repercussions of your changes realistically. A recent message board post I read recently had the warforged stop working the instant Cyre was destroyed, placing the mystery of what animates them squarely in what is now the inaccessible Mournland - and the Lord of Blades knows how to bring them back to life. Just like this, the history of Eberron is yours to change, as are the details.
Another useful technique is to make up your own secrets. Let the players be smug in their knowledge of the book’s game secrets; the secrets in the book aren’t even one tenth of the secrets in your Eberron. So your players know about Oalian, the awakened druid tree. They don’t know that King Boranel’s most trusted advisor is one of the Lords of Dust. Some of the secrets in the book might even be false. Perhaps some of the fantastic things, places and people in the world are just myths, and it turns out that the Lord of Blades never existed at all.
While players don’t enjoy being cheated out of their knowledge, it’s equally poor form for a game’s plot to be spoiled just because some of the players already know the world’s secrets. Rather, your players only think they know the world’s secrets - remember that any of them can be lies, and even so they only know a tiny fraction of all the world’s secrets.