I mentioned not too long ago that I was now hooked on this series. Let's just say that Book 5 has done nothing to cure my new addiction. Can this series keep getting better with every book? I certainly hope so. This time, Amy and Dan are off to Russia. And aside from saying that they face the most fierce danger they've seen yet and uncover what is likely the most pivotal secret in the series, I can say very little without spoilerizing (Is that a word? I guess it is now :D) you for the first 4 books in the series. Bring on Book 6! In Too Deep... coming out November 3rd.