So, recently I watched Death Note. This is one of those series that is like crack, you pick it up and are completely unable to put it down until you're done.
---Spoilers Plz---
Death Note, ostensibly, is about vigilantism. Even if we could kill people as fast as we could write their names down, we still can't change the filthy things about human nature. It's abundantly clear in the last arc that there is still plenty of evil around: the '70%' reduction in crime as Light claimed is basically just a calculation of specific incidents that managed to get recorded. You see a huge mob of people attack the building where N is located, and then suddenly stop when he distracts them with a huge pile of money (and given his wealth, not even very much money was needed). You see sleazy television broadcasts 'proclaiming the will of Kira' with obvious parallels to fundamentalist programs: and why not? If nobody knows what Kira wants, how can they expect to behave the way he wants them to? And yet in the very act of doing so, people are still vile and hateful and everything and pretty much in the same proportion, minus a few thousand.
But anyway, I actually wanted to mention my thoughts on Light's actual masterminding flaw. In the first section of the story, Light manages to kill L and get away with it for only one reason: L could not fathom that Kira would manage to force the hand of a Shinigami to kill him. In fact, the moment that Light told Mira to go and act as Kira on his behalf when they got their memories back, L was in checkmate.
When he goes up against N, he makes a huge mistake: he lets N choose the battleground. Since N basically had all the time he wanted to think about his plan, there is no way that he would make his move before he was absolutely positive that neither he nor the investigation would be compromised. It's all very Sun Tzu.
N approached the problem in such a way that Light could not have layered his gambit any further. In the end: Light was out of resources that N could not predict. Fake notebook? Easy stuff. N knew he could doublecheck it if by touching the real one, he could see the shinigami, and then he could hide his own hand by not revealing that he could until it was too late for Light. So even if Light attempted a triple blinded gambit and went four deep in fake notebooks, none of it would have managed to work because until N got his hands on the real notebook, he would not even be able to move forward with his plan. And even if X-Kira didn't substantially ruin the plan by obviously giving himself away, N would have managed to figure it out then as well.
In short: Light failed to remember there was a way to check that the notebook was legit, and his gambit completly relied on faking the notebook. Against someone like N, the plan was doomed to fail. The only way Light could have won was if he had another rule he could explot that N didn't know about . . . but N knew everything.
Sun Tzu: Engage people with what they expect; it is what they are able to discern and confirms their projections. It settles them into predictable patterns of response, occupying their minds while you wait for the extraordinary moment - that which they cannot anticipate.
Light managed to do it the first time. He thought he was doing it again the second time, but he failed to understand his opponent.
It is said that if you know your enemies and know yourself, you will not be imperiled in a hundred battles; if you do not know your enemies but do know yourself, you will win one and lose one; if you do not know your enemies nor yourself, you will be imperiled in every single battle.