Not sure how many of you guys read manga here but I read a lot I like it better than anime. I mainly read Seinen manga because they are either very mature or very violent and don't get made into animes unfortunately but do get made into Japanese films and dramas which I don't watch.
This is my favorite manga by far. It's about a terrorist/anti-hero named Akumetsu. Basically Japan is on the verge of economic collapse with a debt of 700 trillion yen which Akumetsu claims is the fault of corrupt politicians and bussiness men. The Prime Minister is trying to pass economic reforms but isn't being successful as everyone else is so corrupt and doesn't give a shit about Japan so Akumetsu confronts him and tells him Akumetsu will kill all the corrupt politions and bussiness men and the Prime Minister has a month to pass his reforms and if he fails Akumetsu will kill him too. As the manga goes on Akumetsu brutally murders several people including the treasurer, a police chief, politicians, etc. It's never been released outside of Japan but it's been translated and is on several manga websites you should all read it it's fucking awesome.
http://mangable.com/akumetsu/
This was actually written by a South Korean author but published by a Japanese Magazine. The manga is very dark and has some really badass fight scenes. They made it into a movie which they called blade of the phantom master but don't watch it it's a piece of shit which barely resembles the manga at all. It's set in an alternate feudal Korea where the ruling empire has collapsed and smaller kingdoms have formed and the main character goes around fucking up all the evil kings who've taken power. Yeah I know I didn't explain much but the plot is complex and very good. The manga is great from start to finish I read the whole thing in 3 days I couldn't put it down.
http://mangable.com/shin_angyo_onshi/
This manga is quite bizarre, it's about alien parasites who invade earth and take over peoples bodies to survive. Most went for the brain but one in particular messed up and took over Shinji's hand instead. The other parasytes see them as a threat and start attacking them and they need to fight to survive. It's very violent and very amusing. It's not too long but a good read.
http://mangable.com/parasyte/
A girl is forced to participate in something called the Liar Game. She's given 100 million yen and her objective is to take her opponent's money and win, losers must pay back the 100 million yen they were given. Naturally if they lose the money they were given they go into a shit load of debt and most players chosen were in debt problems already so everyone is quite determined to win and take home a lot of money. It's a zero sum game so naturally if someone wins money, another goes into debt. She teams up with an ex-con who recently got out of jail so she can get out of the game. There is no violence in this manga it's mostly talking. It has the best story out of any manga I've read or any anime i've seen. It's very complex and has a lot of twists. It's still on going and while it's not being made into an anime it did get a drama version (which I don't plan on watching). Very complex, you guys should read it.
http://mangable.com/liar_game/
It's a manga about a mentality disturbed man who assassinates members of the Yakuza on behalf of his uncle who manipulates him. It's extraordinarily violent and very cringe inducing. Do not read if you have a weak stomach. The plot isn't that great but the character development is and everybody is fucking crazy and has awesome fight scenes.
http://mangable.com/ichi_the_killer/
(sorry I couldn't find a better picture)
Holyland is about a teenager named Yuu who doesn't fit in and is bullied a lot. He learns to fight and the only place he feels he belongs is the downtown district of the city which he calls his holyland. He's attacked by a thug and beats him and and then afterwards gets attacked by others. They want to kick him out of the "holyland" but he fights back and beats them. He becomes known as the thug hunter and a lot of people go after him. It's a very thug's life type of thing. It's got drugs, violence, thugs, etc. It has a very different take on Japan and is very good, even a little inspirational. The author tries to make the fighting realistic but it does get a little flashy sometimes but not too much, no swords, guns, or magic/superpowers, mostly hand to hand fighting.
http://mangable.com/holyland/
Did you guys know there was a Battle Royale manga? It has a few changes but it's badass, well written, and has some emotional moments. If you don't know what battle royale is think hunger games but better, also it came out first.
http://mangable.com/battle_royale/
So what do you guys like? Intend to read any of these? Let me know what you guys like and recommend me some seinen manga you know of.