quoted by wikipedia:

20th Century Boys (20世紀少年 Nijisseiki Shōnen?) is a science fiction mystery manga created by Naoki Urasawa. It won the 2001 Kodansha Manga Award in the General category, an Excellence Prize at the 2002 Japan Media Arts Festival, and the 2003 Shogakukan Manga Award in the General category.

Urasawa wrote 20th Century Boys along with another popular title, Monster for 2 years (Monster ended in 2001). It was licensed by VIZ Media in 2005; however, at Urasawa's request, it has been rescheduled for release after Monster finishes its English serialization due to a change in art style over time.[1]

20th Century Boys seems to have been inspired in parts of the story by the works of Stephen King, containing allusions to It and The Stand. However, the story draws allusions mostly from rock and roll, with its title based on T. Rex's famous song, "20th Century Boy".

The last chapter of the story is being serialized under the name 21st Century Boys. Also, a live action movie adaption is planned to be released in 2008, directed by Yukihiko Tsutsumi[2].
Σύνοψη (πάλι quote από wiki):

Growing older is pretty rough and Kenji is finding out just how hard it can be as life starts wearing down on him. On top of trying to make ends meet running a convenience store he has to care for the niece that his missing sister left in his care. Memories of youth make it easier, until those memories come back to haunt him.

Kenji and his old friends are slowly being drawn into a mysterious conspiracy that could threaten the world. Who is the mysterious "Friend" and how does he tie into Kenji's youth? Why are there disappearances and deaths tied into Ochanomizu University? Their memories hold the keys to the puzzle, but time and age have clouded their minds.

The strange occurrences and the reach of the "Friend" conspiracy grow by the day. It will all culminate on New Year's Eve 2000. Will Kenji and the others be able to put together the puzzle and save the world?
Λοιπόν, επειδή εδώ και πάρα πολύ καιρό κανείς σας δεν είχε αναφέρει το καλύτερο manga όλων των εποχών (και το εννοώ), έπρεπε να το κάνω εγώ, μιας που είμουν και ο μόνος που είχε ανεβάσει το τελευταίο volume σε ολόκληρο το internet-μου το είχε στείλει ένας χιλιανός, του οποίου θα του το έδωσε κάποιο team που επιμελήθηκε το scanlation και ενώ όλοι περιμέναν ένα συγκεκριμένο team να ανεβάσει ολόκληρο το volume, για ένα διάστημα μηνών, όλοι οι otakus ανά τον κόσμο το κατέβαζαν από λογαριασμό μου στο savefile. Anyway [/self gloating mode], πρόκειται για αριστούργημα. Αν και όποτε γίνει animated..σκεφτείτε μόνον πόσο γαμιστερό είναι το Monster. Ε, το 20th Century Boys, αν γίνει με προσοχή-και ελπίζω από το ίδιο studio-έχουν φτιάξει και το Death Note- θα στεφθεί αυτομάτως το καλύτερο anime όλων των εποχών.