After reading Divergent and Insurgent (don't spoil it... I haven't read Allegiant yet!), I didn't think I could find a book I loved so much. Boy, was I wrong. This series sucked me in. I couldn't stop reading and I had to purposefully avoid reading the last book since I was moving and job searching at the time and I knew that I wouldn't get anything done once I started the book.
This series contains four books that follow a girl named Meghan. She finds out (in like the first two chapters, I promise) that she is half-fairy. Plus, her little brother gets kidnapped and taken to the fairy world - so she finds her way into the world to get her brother back.
The author crafts a wonderful world that adds modern elements to traditional settings. Familiar characters include King Oberon, Puck, and Queen Titiana, famous mostly from Shakespeare's Midsummer Night's Dream. (Which is another fantastic book, by the way). New characters include Meghan - a confident half-human, half-fairy who fights for her family even when she's weaker than the rest of the fairy world. It also includes Ash, a cold ice prince from the Unseelie court, and the Iron King, who seeks to destroy the fairy world as it stands.
The books in order are Iron King, Iron Daughter, Iron Queen, Iron Knight. The Lost Prince is the beginning of a new series that relates to the first four books, but isn't directly connected. I still have to read that one!