Out of the many anime that i've watched till today (including Code Geass) this one tops the list.

you will find reviews which say that the second half of the show is not good, but that is just half the truth.first off the show starts off brilliantly awesome. i can bet you ,if you like thrillers, just watch the first 2 episodes and you will be forced to just go on watching it. the first half continues to be amazing and the show just gets better and better and better.....

now when i say that first half is simply awesome, it doesn't mean that the second half is BAD. the truth is that the first half is just so consistently mind-blowing. there comes a huge plot twist after the first half , and you think -"can the show go on with the plot twist". well it doesn't . but the plot twists again and we're back to where we were.but we land up with another(even major) plot twist) and show loses its charm a little.new characters are introduced and by the time you get used to those new characters,the show ends.but the ending emerges as ,lets say, as good as the beginning.

so it is only fair to say that the second half is irregular (and not bad).one more thing -YOU DO NOT WANT TO MISS THE AWSOMENESS OF THE FIRST HALF.it is far more mind blowing than anything you can imagine.

Conclusion-go for it you'll be thrilled for the first half, might be off for 5-8 episode , but in the end you might as well want start watching the show again.