Thoughts
The thing that Ancillary Justice did, that so few stories do, is that it doesn’t tell the reader everything that the main character knows.
A lot of books infodump the entirety of the main character’s backstory and knowledge (and good books—The Hobbit does it, Harry Potter does it, etc). This formula works, because as the conflict and the plot develop, the character’s understanding and your understanding move at the same time, all 4 in lock-step. (e.g. you see someone tell that main character that there’s going to be a murder, and conflict and the plot of the book become about stopping the murder.)
But it becomes formulaic. It limits your ability to introduce new information throughout the book, because it’s difficult to introduce new plot 3/4 of the way through the book.
There are of course ways to separate them, but they’re very difficult to do. Maybe Ancillary Justice is an exception, but I conjecture that withholding information about the main character until just before it’s relevant (just before, not when it’s relevant, if you introduce it when it’s relevant you’re back to trying to do everything at once again), is one of the easiest ways to do this. You don’t need to understand the conflict or the main character in their entirety in order to start reading the book.
Anyways, finished Elantris; very hard to rate after reading Ancillary Justice. Sanderson throws new stuff at you and the plot and the characters and the conflict 95% of the way through the book. Literally 20 pages left. 4 stars, ultimately the characters save it.