Awesome and realistic high school+shounen+mystery, based in a present time, is quite a rarity. Usually mangakas either go the supernatural route ( for example Psyren, Future Dairy, Death Note ) or give up on high school setting, and change into seinen instead ( like Remote or Angel Heart ). Bloody Monday, while maintaning the image of characters being "extraordinary", still manages to pull a captivating story.
Story - 8/10
All of it starts with introduction of a genius hacker, Falcon. For a moment there, we are lead to believe, that the story might go the very cliche "villain of the week course". But it takes just one chapter for the engines to start up, and very soon we are taken on a high speed rollecoaster, with traps, battle of wits and load of plot twists - some of them unexpected, some of them annoying.
Author not even for a moment let us have a grip on the overall situation. The moment you think you know, what's the sides looks like, someone turns out to be a traitor. The victory in one chapter, might turn out to be unexpected loss 20 chapters later. If that's not enough there can always be new information, new person appearing, new threat, new encounter... But even with all that constantly twisting plot, overall the story seems quite coherent.
If I have to compare this manga to something, the closest would be american series "24". The combination of personal grudges and terrorist objectives, involvment of main characters family, betrayals and desperate battle against time - those are characteristics of both of those titles. Another similarity is short period of time, during which all the incidents occur. The action, that takes place in manga, is resolved in few days ( I wasn't curious enough to count exact numbers, but I'd estimate the whole course = 2 weeks).
Art - 8/10
The drawing style is really good and fits the slightly dark overall mood. Characters are detailed and good looking, scenes are filled with suspense, emotions and action (depending on which one is needed at the time).
Characters - 7/10
As a Shounen manga, Bloody Monday have characters that are really appealing.Through their actions, speeches and looks the really make this title a very enjoyable reading experience. So why I give it only score of 7? Along with Shounen advantages, this title have some of the shounen flaws - those characters lack depth. Fujimaru have barely any growth, even though he is suddenly in the middle of really bloody mess. Otoya, apart from his role near the end, just acts like a sidekick. There is some mentioning of Aoi having crush on either Fujimaru or on his father, but that is neither properly used as a motivator, nor resolved at any given point. Basicly there is lots of "cool characters", that fit the story well, but they aren't exactly alive.
The enemies rank slightly better in my eyes. They aren't just bunch of evil, obsessed madmans (well some of them are :P) , but have convincing goals and motivations. From the money driven hitman, through people wanting to get revenge on the country up to the religious fanatics - each of them has their reason, to act the way they act.
And as a last note - Haruka is just an annoying baggage. Her only purpose through the manga is to get kidnapped and rescued (and since she has kidney problems the rescue need to be fast).And as if that wasn't enough she also like to put herself in the middle of danger, "because she can't leave onichan alone".
Overall - 8/10
This manga have it flaws, but which manga hasn't got any? If you like a good thrillers, you won't be disapointed. This title is very enjoyable combination of high school shounen and intelliigence agency vs terrorist story.