The lost princess of a magical kingdom and her soulbound guardian are meant to be together. Unfortunately the princess has powerful enemies and a very self destructive personality. Much as her guardian loves her, there is only so much she can do to protect her from evil and herself.
I reviewed the first book here, and it follows on very well from it. It's a much stronger book, in story and characters, although it has a lot less world building because most of that has been established. Which means you're probably best off starting from the beginning. Actionwise, not a huge amount happens. The plot is quite clearly a three parter, and this is the "Empire Strikes Back" episode. Again, you should probably read all the books in a row.