Boxers and Saints by Gene Luen Yang
It's a little hard to articulate but what I liked the most about this story is also what I simultaneously found to be the most confusing aspect and what I wanted more of, the character's spiritual lives. Both of our leads seem to be seeing things that aren't there, the gods of the opera and Joan of Arc, and through them knew of things they shouldn't have had any way of knowing. Up until the end of Saints it didn't bother me if they were real visions/things or not, it didn't matter since they were there for the story and that's that. But then at the end of Saints we get a few weird, hints, like the fact that some of the symbolism that was very specific to Boxers suddenly appears and merges with the symbolism that was very specific to Saints and there's an almost throw-away line that's sadly just a tad too spoilery for me to quote here. This intertwining mysticism was the most interesting part of the story for me and I wish it had either been explained more or hinted at earlier but I suppose if that had been the case then it would have made one or both of the characters' conflicts look "wrong" and that would have hurt the story far more than it would have helped it.
One thing that struck me about the story when I was writing the review is how well-balanced the story really is, every element seems to have either an equal or an opposite in the other story yet it's not written so obviously that it seems like Yang was following a formula. In Boxers we have a young man who is accepted by his family and told about strange powers (which only then come to him, debatably of course based on how you interpret all the magic in the story) and in Saints you have a young woman who is ostracized to the point of having no name and yet seems to have real, religious visions many times through the story. Boxers is much longer, I was surprised how thin Saints was by comparison, but I feel that both of them were just the right length for their part in the story and that yes you could probably read them separately if you wanted (I advise against it and I also advise against reading Saints first because of that ending but readers should already know my opinions on reading books out of order anyway).
The art in B&S helps support the story very well even though the art is relatively simple. It helps keep up the mystery about the religions by showing each book based on how the character perceives it, Little Bao sees his gods while Vibiana can see Joan and yet the fighters appear as ordinary, but still terrifying, peasants, nothing like their superhero-esque gods. Interesting enough the color palette for both books remain muted, while the gods of the opera may have much more colorful outfits the tone of the colors is still subdued, just like how Joan appears wreathed in gold but it's not a brightly polished, glittering gold. It's interesting to note how down to Earth the colors appear when all the characters claim intervention from a higher source but I think it was a very good choice.