There are two Iron Fey novellas available as e-books which fit nicely in the series as books 1.5 and 3.5. They don't take long to read, and if you picked them up when they were first available they were free on Kindle (but Winter's Passage is now $2.39 but Summer's Crossing is still free)! Because they're so short, I'm including them both in this review post.
Winter's Passage (The Iron Fey #1.5) by Julie Kagawa
Released: May 20, 2010
Meghan Chase used to be an ordinary girl...until she discovered that she is really a faery princess. After escaping from the clutches of the deadly Iron fey, Meghan must follow through on her promise to return to the equally dangerous Winter Court with her forbidden love, Prince Ash. But first, Meghan has one request: that they visit Puck--Meghan's best friend and servant of her father, King Oberon--who was gravely injured defending Meghan from the Iron Fey.
Yet Meghan and Ash's detour does not go unnoticed. They have caught the attention of an ancient, powerful hunter--a foe that even Ash may not be able to defeat....
I didn't realize that Winter's Passage existed until I went to pick up Summer's Crossing.... only to realize I had missed one. And I had meant to read them all in order, sigh. So I picked it up and read through it quickly anyways.
Since I've been reading through the series so quickly, I had a hard time remember which events occurred in which books. But Winter's Passage seemed to have a few flaws in my opinion. There were just a couple things that happened that didn't make any sense.
First of all, how come Meghan was able to use summer glamour here without getting sick? At this point, she's killed Machina and absorbed the iron glamour... right? Am I just missing something? This part just didn't seem to flow with the rest of the series. But I could be completely wrong on this one.
I also didn't see why Ash kissing her would save her from freezing to death. I'm sure it would surprise her- but still, she was passing out from the cold. I just couldn't see how that really made much sense.
I did like being able to read about how Ash and Meghan came to the Unseelie Court and what happened in between books 1 and 2. It felt like a little bit of insider info, which would be enjoyable to those who are fans of the series.
Summer's Crossing (The Iron Fey #3.5) by Julie Kagawa
Released: June 1, 2011
A Midsummer's Nightmare? Robin Goodfellow. Puck. Summer Court prankster, King Oberon's right hand, bane of many a faery queen's existence—and secret friend to Prince Ash of the Winter Court. Until one girl's death came between them, and another girl stole both their hearts.
Now Ash has granted one favor too many and someone's come to collect, forcing the prince to a place he cannot go without Puck's help—into the heart of the Summer Court. And Puck faces the ultimate choice—betray Ash and possibly win the girl they both love, or help his former friend turned bitter enemy pull off a deception that no true faery prankster could possibly resist. I haven't started reading The Iron Knight yet (I start that tonight- yay!) so I can't speak to how well Summer's Crossing fits in between books 3 and 4.
What I can say though, is that Summer's Crossing is a fantastic novella told from Puck's POV; and I'm sure you can imagine how much fun that is to read! I really liked how Kagawa revealed a bit more about Puck's feelings and the inner struggle he seems to be facing at this point in time in regards to the relationship between Ash and Meghan. It really added more depth to his character, being able to see that it isn't always fun and games with him.
It was also neat to see the relationship between Ash and Puck a bit more. I think we get a better sense of how they used to be friends, since most of the other books have been focused on them trying to fight each other constantly. But you can see that there is an underlying trust between them, that isn't found between many Fey at all.