As the title says, this book deals with the apprenticeship of the mages. All 4 years of it. Yes, Ryiah is 16 at the start of the book and it ends with her being almost 20. There is a LOT happening in this book because of that. 
 Each year, all the apprentices from every "class" are posted on a certain location to train and help the commanders. Before going to the academy during mid-year, they all participate in a brutal mock battle where they can practice and show their tactical, magical and physical skills. I loved those battles, they were my favorite part of the book. During their stay at the academy they have the winter ball and at the end of the year they attend the ceremony where fifth year apprentices become mages. 
 While they are in the postings, there are some attacks suspected to be organized by a neighboring country creating tension and real battles where we get to see the reaction of the apprentices. The attacks are brutal, don't expect a happy go lucky kind of fight. 
 There is also a lot of time spent exploring the relationships between the characters. There is romance, break ups, friendships put to the line, betrayals, and more. There is also an infamous love triangle, which I didn't like. I'm not very fond of them anywhere so it is nothing particular of this book. I was angry at Ryiah for not deciding and making the two boys suffer. 
 The other thing I didn't like was the amount of years the book encompasses, all 4 years of apprenticeship. It was difficult to keep track of time, sometimes an event would happen and a couple of chapters later I found myself thinking "Wait, have 6 months already gone by since THAT?". I didn't think the characters changed much in that time, which I found a bit distressing. 16 year old Ryiah acts the same as 20 year old Ryiah. 
 The ending was heart melting! (view spoiler)[ It was a long shot for Darren to pursue for 2 years a way in which he could end his engagement without putting the country in a difficult position in the upcoming war. It shows how much he loves Ryiah and I don't know how she didn't jump from her chair and hugged him in front of everyone. I know, she was confused, but I wouldn't have blamed her. (hide spoiler)] 
 Despite everything, I enjoyed this book a lot and I can't wait to read Candidate which comes out in a couple of weeks.