Honestly, if I remember correctly, every book is pretty muich better then the previous one. Again, I read them the first time about 3 years ago, and haven't read them again till now. And, I've read 60+ fantasy novels since then, so my memory of the books isn't the best right now.
However, I remember loving every book, especially book 2 on. Book 2 really had me hooked for good. If book one seems fairly simple or mundane, book 2 gets awesomely better and more action packed.