Gosh, I don't know how ib did it. It had all the elements that I ostensibly didn't like (in particular, the antihero protagonist who wants to destroy the world), but ib makes everything work, and work really, incredibly well.
I loved ib. It was fantastic. Probably one of the best things I can remember reading in recent years. The lines were poignant, the character conflicts fell on just the right side of painful, the art was wonky occasionally, but when it worked, it worked.
And, in their final comments, the author notes that ib is their "life's work," and it definitely shows. The whole thing is just so earnest, and this earnestness really comes through that, even with all its flaws, I can't help but cheer both the mangaka and the characters on. It's definitely a work that I would love to see them revisiting, if only to see how much they have grown as a person. (Because ib definitely feels like a personal reflection above all else, and that's definitely part of its charm.)
I've seen some people dissatisfied with the ending, and it did feel slightly strange to me (it's clear that it was a premature ending and that there could be more to come), but I still enjoyed it regardless. For a series of this scope, it almost felt like any ending would be disappointing, and the fact that I wasn't disappointed by that ending, no matter how truncated it is, says a lot about the mangaka's ability.
I'm definitely looking forward to their future in the manga industry, because if this is their first work, then who knows what other amazing things will come from them.