Death Note and Monster are two great psychological sagas, both running over 20 volumes, if I remember right. Death Note is about a nondescript high school-age Japanese genius, son of a police chief, who stumbles across a notebook one day, one which enables him to kill people by writiing their name in it, with certain restrictions. The entire series is a cat-and-mouse game between this guy, Light, and the various forces who set out trying to discover who and how has suddenly taken it into their head to start remotely executing criminals.
Monster follows a Japanese surgeon working in Germany who after saving a politician’s life at the hospitcal in favor of a child’s one night, when next faced with the same choice disobeys orders and saves the life of a child. People around him start dying, he ends up eventually coming under suspicion, and it goes from there. It’s written to be realistic inasmuch as nothing supernatural happens. One of the best ones out there.
Please Save My Earth is a 6-volume work centering on a teenage girl and her boy neighbor. She and some others start remembering a past life living in an alien research outpost on the moon. The sci-fi element is actually fairly low-key, all things considered, and the narrative follows the interactions among six normal people who have to deal with the memory of past lives lived together, and particularly the young neighbor, who is far too immature to handle the memories. It is generallly agreed that the series somehow manages to convey an intense nostalgia and sentimentality, despite none of its readers ever having lived in a research station on the moon (I am unsure whether this one has been released in the US).
I will add more as I recall them. The three above are remarkable and thus recommended.
I generally like things that are relatively lighthearted (though serious is good sometimes too). Thanks for the recommendations.