Not an overrated masterpiece but clearly a hollow one.
When the MAL user oOoOoOo wrote this in his MW review:
"While an interesting character sketch, I cannot say much for the story itself. Machinations and dramatic events often seem forced and unrealistic, compared to the more carefully plotted mysteries of "Monster"."
I have to admit I couldn't remove my bias even before I completed the first arc/chapter/plot event. (The way the story is told is via one huge epic. This could just have easily been a Resident Evil type of game, a film directed by Kubrick or a crime thriller novel and thus normal manga reviewing aren't as relevant to grasping the quality of this series)
In that initial bias, I so wanted to shout "overrated" and how this was another fake Hollywood made serial killer story and I dearly wanted to write a counter rebuttal to the above reviewer stating scene for scene why Monster's plots are more unrealistic, unlikely and forget forced - the characters literally are supermen who don't die and how reviewer keasty was right.
Truth of the matter is though, it does hold a certain charm. A certain finesse. It's probably even a better researched or recreated world than your average quality manga. The artist or the writer isn't very shy in creating the type of epics that would sell well towards those seeking a more defined taste of entertainment in their medium. In that sense it's very high quality work in the sense that the locations and the places are all different and the characters literally move everywhere in the world and they were able to avoid the repetitiveness of focusing on only one or two generic characters. In that sense, keasty might have undersold the idea of a mature Ash Ketchum hovering around the world. This is not your typical rpg or battle manga setting, every new location contains detailed minor characters.
I do however disagree with his review when he says this is more mature. No, the good doctor doesn't help solve anything. Your typical dark Batman strip or even Pokemon attempts to solve more mature problems than the main character in this series. Where it's able to disguise itself as a mature manga is by utilizing many of the same caricatures Award-winning Hollywood films utilize when creating a dark tortured character. Maybe slightly more original but not too much. Think Rambo + Jason Bourne + a doctor that's on par with Black Jack or House but dealing with less mature medical events and mostly involving him using his skills to win over common friends (who happen to be not so common)
It's this element that makes Monster a disappointing manga for those who are looking for a mature themed manga. The Emperor's New Clothes are there but in the end the main protagonist could just have easily disguised himself as the antagonist and the only difference in their heroics is his medical ability. (Which believe it or not is his trump card even at the end. You could even consider this manga a how to guide on how to conquer the world via reciprocity. It's all very Hollywood propaganda-ish like that - although I'm not claiming this manga is maliciously made - it's just cheap like that. The type of pseudo-intellectual inducing scenario that makes it sound original until you realize the lack of depth/strategy or actual background behind any of the events)
What makes this "un-overrated" though is that despite my complaints above, the middle point of this manga is mostly revolving around a conspiracy theory and in that aspect it's very good at playing with the whole Hollywood scenario. Think of it like a dual paradox. What I just wrote above complaining about is at the same time what the plot is addressing on the mystery side of the issue. It's very "plot within a plot/complaint within a complaint" like that and for that it is able to paint an epic semi-realistic dark fantasy that is only broken by the overall merging of all the elements.
In the end, read this manga only if you are planning to complete it. Regardless whether you hate the beginning or the middle or found this to be too long - you've just wasted your time if you don't do this. Treat this like a movie - if you're not willing to watch it till the end - you'll miss out on why you truly hate or love this and all you get is just one whole filler manga. Not because the ending ties things all up but because like a movie the first two stages are worthless unless you reach that 3rd stage of the plot. If you're not able to do this, well I'm not saying the manga couldn't be better in your eyes as the final product does take away many charming elements but suffice to say you won't really be able to fully understand the "canon" of this manga. (although honestly I was bored to tears by the whole series that I didn't bother to check out the novel with the epilogue interviews)
For those still unsure, my hint for why the latter parts of Monster are necessary revolves around a certain dark fairy tale artwork. If you like puppet master types of conspiracy - Monster doesn't have the detailed bite but it does possess one of the better barks. A bark that's good enough to judge this as a whole regardless of how silly/immature/disappointed you are with the series so far. Think of it as finally witnessing the "Monster" although not in a scary but interesting manner.
All the rest? Well, here's a summary of what makes Monster fake and Hollywood only:
-bad psychologists (not even if you don't know anything about psychology)
-super doctor (with little to no medical drama scenes to justify this)
-unrealistic mystery (literally it's one whole chase scene - the mystery revolves around the antagonist already being established in the seedy underground even though it's very unlikely that he should have gotten that far already even by fantasy standards)
-Hollywood minor characters (if you thought Hollywood protagonists were bad enough, the minor characters often edge them via doing some of the most ludicrous ways of surviving and I'm not even referring to those who get lots of return cameo scenes. Even those who died, you can't help but feel after the first couple murder scene every death becomes more and more stupid)
-It could have been way way better and more and more mature if only... (Again going back to MW, part of why it seemed realistic in MW despite it being fantasy was the viciousness and unpredictability of the deaths. Anyone who knows anything about serial killing knows it's the unlikely candidates that make the killings that much hard to locate. Even in terms of fantasy morality, Light Yagami of Death Note fame for example had more caution and strategy than the antagonist of this series even though there's barely any fictional super-weapon in this series and yet the antagonist is able to survive this far and this long. Finally characters are too sensitive despite their hardened background. If MW was preachy because of Tezuka trying to hone in on the severity of the events happening on the characters, Monster is preachy in the opposite manner. Guys have life changing moments despite the scenes being generic and yet they shit on their own revolutions one arc later once the plot doesn't call them to be relevant towards that previous scene anymore. It's like three dimensional fictional characters becoming two dimensional because instead of fully continuing character development - it's all this arc - growth - stop - next arc - growth and then stop and there's no rinse or repeat. It's all intended canon ending up being fillers not because it took too long but because it kept resetting the character's development.)