3.5 stars. 
 Gods, this book was so much better than I first believed it would be. I never cared much for Ash during the first three books. That changed a little. 
 Ash grew on me, a lot. I was starting to understand some of his actions and reasoning during book 1,2 and 3. But... then chapter 17 happened and I knew once more why I disliked his persona. I'm sorry but I cannot 100% see through that past .(view spoiler)[ I'm sorry but making girls fall in love with you, have sex with you and afterwards break their hearts by telling them it meant nothing too you? That's not a past I want to see for the MC's love interest. (hide spoiler)] 
 HOWEVER, Ash did go through a lot in this book, and even realised he would have to live with all the mistakes he'd made in the past.Luckily these mistakes were not brushed aside, as I feared they'd be. No Ash would have to life with what he'd done and come to peace with it (if he ever can) 
 Now for the story itself... I loved it. I have always loved stories involving quests, riddles, you name it. And this book was no exception. Ash made a promise to Meghan to find a way to be with her. So he starts a journey in which he goes to find the End of the World in hope to gain a soul there. When he reaches said End, he must endure a gauntles and three (cruciating) trials to gain this soul so he can become human to be able to be with Meghan in the Iron Realm, without the iron killing him. 
 And of course, Ash will no endure this journey alone. Puck and Grimalkin return in this story and they made me laugh so much. I've loved them both during the first three books and they are still as funny and adorable as they were before. You find out quite a bit more about Ariella, Ash's old love, and the feud that has been going on between Ash and Puck for decades. 
 Oh and.. a certain Big Bad Wolf joins the picture too... He's brutal, powerful and a little scary. Wolf fits just perfectly into this story, if you ask me. 
 Honestly I loved the journey and the characters. I wish I'd loved Ash more, but it is as it is. 
 All in all, I really enjoyed the Iron Fey Saga and it will receive a special place in my heart (and Puck will steal most of that space)