DIA is very different to the first book, I think. In pace and also plot wise, as you might have found in the differences between S1 & S2. The difference is there's still quite a bit of shagging in DIA, compared to the drought that we seem to have had in S2.
The book is ok. I'm not overly enamoured with the books. And they go downhill after Drums Of Autumn in my personal opinion. They weren't what I hoped for after watching S1. I've enjoyed the discussion and speculation on the other thread though.
I'm not entirely sure, but I think the new book that's coming out is the last one in the series.