For one thing, the stylistic theme of the whole affair can only be described as "surreal". An interesting mixture of clown motifs and religious themes sets this anime immediately apart. The primary villain manages to be simultaneously comically ridiculous, incredibly sinister, and utterly evil, whilst the main supporting villains manage to be extremely likeable characters with a very human side, even whilst doing their master's undeniably evil bidding. The more generic enemies – the Akuma – are consistently creepy enough to maintain interest. I mean seriously. Creepy.
Characters and their abilities are also very well-executed. Unusually for a shonen, the main character is actually both interesting and likeable enough to deserve all the focus he gets; indeed, I think one area this anime succeeds brilliantly in is balancing its cast of characters. One never feels like the cast is getting stale, but at the same time it never seems to grow too large; characters get pretty much exactly the volume of screentime they deserve, and the characters who receive the most focus are generally also the most likeable. I say this in direct contrast to anime such as Bleach and Naruto, which have a huge cast of secondary characters, many of them more likeable than the main characters, but they have a distinct tendency to fail to receive any development, or often even any screentime whatsoever.
The story itself is somewhat episodic. It manages not to shy away from focus on the main villains from very early on, whilst at the same time maintaining a healthy air of mystery and distance about them. Overall, it avoids the classic shonen trap of feeling like just a sequence of battles; with one major exception, progression is generally more complicated than simply battling enemies. The shonen "power curve" of progressively stronger enemies as the protagonists' power increases is present, but never feels forced; "evolution" is treated as an important theme, and often used to draw uncomfortable parallels between the heroes and the villains. The author is also not afraid to give a fair amount of focus to the characters without special abilities. Comedy is present, but generally restricted to short, more light-hearted "relief" segments in between the main story arcs.
But where the series really shines is in its emotion and conflicts. Enemies are routinely treated as sympathetic in one way or another, and the protagonists' "heroic" organisation is itself by no means morally perfect. The war with the Akuma is presented as just that – a war, and generally a losing one, with all the tragedies and internal/moral conflicts that come with that. Whilst the series doesn't have a habit of killing off its central protagonists, tragedy and death are central, recurring themes from the very first chapter.
Overall, I find D.Gray-man a compelling and entertaining series that is well worth a read.
(The anime had a premature ending, therefore I would suggest continuing D.Gray-man on chapter 156)
