Yuukoku no Moriarty is an unconventional re-imagining of the classic story, with Sherlock's arch-nemesis as the protagonist. For better or worse, the author didn't have the courage to go all out and keep him a self-serving master of crime. In this version, Moriarty is an underdog who goes from rags to riches, and grows up to become a merciless vigilante on a crusade against corrupted nobles.
Incredibly cheesy, right? Yes, of course, but not without potential for some nice, juicy moral ambiguity. Does the story deliver on that front? Well... yes and no. Kinda.
You see, Yuukoku no Moriarty can be split into two distinct parts:
the fun one, and the NOT fun one. The manga is at its best when it focuses on Moriarty vs Sherlock mind games, and at its absolute worst when it focuses on our protagonist fighting evil nobles. And they are eeeeeevil, all right. Evil with a capital E. But, first things first, lets start with the good part.
Moriarty and Holmes are both compelling characters. One is a ruthless, brilliant and charismatic killer, but driven largely by compassion for the oppressed. The other is a likable and eccentric genius detective, who sees solving crimes as the best source of entertainment. The two are excellent foils for each other, and their antagonistic relationship is the manga's strongest point, even at this early stage.
Other characters are also an interesting bunch; from Moriarty's cold hearted brother who idolizes him, to Sherlock's upright buddy Watson, we have a great variety of personalities.
So... let's get to the “not fun” part now, shall we?
The chapters that don't deal with Moriarty vs Holmes, have villain-of-the-week structure. It usually goes like this:
1. William (Moriarty) learns about some crimes committed by an evil noble.
2. He investigates.
3. He and his sidekicks easily kill the evil noble.
4. Rinse, repeat.
Those minor antagonists have exactly three roles to play in the story: being cruel to commoners, gloating evilly, and getting their asses handed to them by our anti-hero. They're completely one-dimensional, they're pathetically weak, and they NEVER pose any threat to the protagonist. Writing them that way not only undermines Moriarty's moral complexity, but also ensures that he has no credible challenges to face, other than Holmes. As a result, you can tell at once if the chapter will be entertaining or not by checking if Sherlock graces it with his presence. If he doesn't, prepare for the pure snore-fest of God Mode Moriarty, offing one-note baddies without breaking a sweat.
Keep in mind that this is a rather new manga and only 16 chapters are available for the moment, so there's probably a lot of time left to iron out the kinks. So far, I think that the good bits make it worth putting up with the bad ones. Despite its flaws, I recommend Yuukoku no Moriarty, especially if you're a fan of Death Note and/or Code Geass.