It's hard to believe how well this was put together at times. I'd say the first 10 episodes are definitely the best, after that the story line has reached a point where it's less exciting. That doesn't mean the rest of it is bad though, not at all.
One thing that striked me is that there were often tensions moments when Light get's interrogated. Ever time when it seems like he's getting caught he comes up with another waterproof lie/alibi to trow off any suspicion. Which is what I meant by the first sentence.
I actually got a Death Note book as a gift after I finished the series :)
One of the most perfectly interlinked and suspense TV show I have ever seen..
