My reading was all messed up because I found 'The Iron Knight' first at a used bookstore. Big mistake. The emotional weight of Ash's journey meant nothing without the context of the previous books. So, lesson learned: follow the numeric order implied by the titles. First, second, queen, knight. It's a straightforward progression. The later 'Traitor' and 'Warrior' are clearly a new set, so read them after you've fully absorbed the first four.
A pragmatic tip: the ISBNs or series numbers on the book spines often tell the order. For the central storyline, collect the books numbered 1 through 7 in the overall Iron Fey universe, then continue with the new sequence starting with 'The Iron Raven'.
I've seen this question so many times. The answer is always the same: publication order. For the Iron Fey world, that means starting with 'The Iron King'. Follow it with 'The Iron Daughter', 'The Iron Queen', and 'The Iron Knight'. That concludes the first major story arc.
After that, you move to the sequel series, beginning with 'The Lost Prince', then 'The Iron Traitor', and finally 'The Iron Warrior'. Reading them in this order ensures you get all the character introductions, world-building, and plot twists as the author intended. It's a seamless experience that way.
It's all about the climax. Each main novel builds to a huge, realm-shifting climax—a battle, a coronation, a sacrifice. Each novella builds to a much smaller, emotional climax—a confession, a realization, a promise. That's the clearest separation in terms of narrative structure. The novels change the status quo of the world. The novellas change the status quo of a relationship. Both are valuable, but they operate on different scales. When recommending the series, I tell people the main novels are the 'what'—what happens in the war. The novellas are the 'why'—why the characters fight the way they do. You need the 'what' to follow the story. You want the 'why' to care about it.