Phoenix
Osamu Tezuka’s Phoenix is the greatest unfinished work in comics (and a real contender for comics’ greatest work of any kind). Don’t let the lack of a conclusion put you off – each volume is self-contained, though there are gains to be had from reading them all, in that characters recur, as do the central themes of reincarnation and questing for immortality, all centred on the mythical bird of the title, whose blood allegedly confers immortality.