The animation is very western, and doesn't really give of a anime feeling. Since the anime has no unrealistic aspects (it could easily have been a live action) the animation style suits this anime very well in my opinion and gives off the ideal vibe for it's story. The animation is a bit flawed when it comes to fluency though, actually outright lazy at times, but the amazing writing and characters more than makes up for it.
To the story at hand, it is easily to me the best one in any anime, and I could argue that it might even be the best story among none anime aswell. It is truly, in lack of a more powerful word, epic. It manages to be absolutely phenomenal at the psychological, mystery, thriller, suspense and dramatic part all at once, involving a large amount of characters who all tie together the story ingeniously.
The main and side characters are beyond this world, and characters that only appear for one episode or so can often have more characteristics and personality than the main characters of other animes. The characters, together with their dialog, are in my opinion the strongest aspect of Monster. The English dub is, beside some bad child voice acting from time to time, VERY good. It is one of the few that are actually better than the native Japanese. I would strongly recommend watching this in the dubbed version, the voice actors has made a superb job in catching the essence of the characters.
I was at many times during the anime completely overwhelmed at how good it actually is, since it's long length I took quite a lot of pauses during my time watching it (watched it over a 3 month period) but every time I picked it back up I immediately remembered why it was so amazing. I doubt that I will ever find any anime better than Monster. It has hit perfection.
A must watch. Do not be scared of the length of 74 episodes, you will be a changed man for the better after watching this. It is a show truly worthy of everyones attention
