This is the novella about the events that take place between The Iron Queen and The Iron Knight (the third and fourth books respectively) in the Iron Fey series. Summer’s Crossing is only about 72 pages long, but it really is an enjoyable read, especially if you’re a fan like I am. Here is a link to the PDF where you can read the book online. But be warned, it’s only free for a limited time!
And if you’re in a romantic mood, check out An Iron Fey Valentine (PDF), a short story written by Julie Kagawa about Ash and Meghan’s first Valentine’s Day together. I wouldn’t recommend reading it unless you’ve already finished The Iron Knight, since it is a spoiler.