Queen Michael said:
I just finished the latest Billy Bat book, so now I need some new seinen to read. What I need is something story-driven, that's cleverly written[footnote]That is, none of the usual obvious padding and a story that's made up as they go along[/footnote] and not an action series.
Well, it depends on how dark your willing to go.
Narutaru is a excellent manga, one of the finest I've ever read. It starts of as a kind of light hearted mon series and... becomes rather dark rather fast. I had a few issues with the plot, but it had, hands down, some of the best character development and character relationships I've seen in any manga, period. It also did a good job of balancing the humor and drama. The second half really took off, and I loved the finale. This is a series that really flew under the radar, which is too bad, given its immense quality. I can't recommend it highly enough.
Bakurano Ours. It's by the same guy, though I'd argue it's not as dramatic as Narutaru. A group of kids have to pilot a robot to defend the earth, but the catch is that the pilot dies after using it. It's a rather sober series, and the character development is, again, excellent. Unfortunately, because there are so many characters, and because there are so many casualties, you don't get to spend as much time with them as you do in Narutaru. You have to view the series as a metaphor for terminal illness to really appreciate it. It's not really about the plot. It's about how completely different people deal with death in completely different ways. This is the story that loosely inspired Puella Magica, if that tells you anything. Certainly not for everyone, but it is good.
Berserk gets a mandatory recommendation, as I don't recall whether you've read it yet. You probably have, but all the same, this is probably the best fantasy series I've ever read.
I will note that the above stories are all INCREDIBLY dark, and not for everyone. Unfortunately I'm not well versed in Manga. Vinland Saga reads like a poor mans Berserk. It's not nearly as dark, and it's a decent action series. Otherwise there's Akira, which is much better then the film.