Most people say death note is a brilliant game of wits.
They say its morally grey.
This is both wrong. All the mindreading is unrealistic. Even if you are the smartest person alive you cant make predictions about other people with 100% accuracy because in the real world you deal with incomplete knowledge. All those "i know that you knew that i knew that you knew..." stuff is entertaining but not "brilliant".
That the series is morally grey is absurd. Yes there are a lot of Kira followers in the manga but most of them are depicted as imbeciles. The only important characters that sympathize with Kira are Misa (who is portrayed as dumb, superficial), Matsuda (also dumb) and this greedy sakura journalist.
In the end Light gets mad. And even in the beginning he starts killing nonmurderers, its pretty clear that almost everyone finds that wrong.
The story is also build on a lot of conventient coincidences, for example that the police chief is the father of Kira, that Misa is in love with Light, that Rem cares way too much for misa and so on.

Light is an empty character, he has no hobbys, no interests,is asexual, he just does what you should do in japanese society, study for school. The only personal thing we know about him is that he played tennis in the past. I dont find it plausible that such a conformist would try to change the world so radically.

The thing i really liked about death note is Ryuuk.
We live in a world where everyone tells us how important it is that we personally take action, that we go vote, that we make the world a better place and such.
Ryuuk just watches, he rearly gets involved in the plot. He doesnt judge. He just enjoys the moment. In the end both L and Light lose, both lived not in the moment but in the future, in their worlds of anticipation. Rem let herself in in lights sceming, that ended in her dimise. We all should be more like Ryuuk and less like Rem. We shouldnt take life too seriously. We should stay in the present. In the end all the planning will be in vain.