I havn't read the book in a long time. So I would like to know what the central theme of this book is? And what are the secondary themes?

I remember I liked how the main character ended up in another world a lot like the characters did in the Chronicle's of Narnia. I suppose this doesn't count as a theme. It is just a similarity between fantacy books but I do not want to be too picky with what qualifies as a theme.

There are many themes but the one that resonated deeply with me was the theme of change. To be precise, the main characters grow and become the best versions of themselves. Tessa realizes her full potential as a scribe, Raif regains the honor of brotherhood, Cameron matures and grows wiser, and Angeline finds an inner strength that she didn't know she had before. It's this unfolding of character development that adds to the heart of the book--it makes you fall in love with them and care for them very deeply.

Actually I have found this to be true in many of Ms. Jones's books. There is something beautiful and admirable in all her characters, with all their vices, flaws, and faults. Although you may not like them or approve of their actions, you can't help but feel connected with them on some level.