The manga isn't as problematic as the anime (even though the problematic content is minor), but because the series has been so inspirational and many of the tropes have been used in numerous media, this series today can come across as underwhelming.

There are a couple of fat-shaming jokes in the side stories, and there are also some astronomical inaccuracies (more from lack of research than scientific improvements over the years), but nevertheless, it was one of the gateways to manga for me, so I will rate it highly for nostalgia purposes.

I'm reading this while waiting for the next anime season to be released, to remind myself of what happened so far.
ngl this series is pretty deceptive, in a good way. Even with the anime, I wondered to myself beforehand, 'How can a story about volleyball be so thrilling and exciting?' I thought the same about the manga, since there is no crisp and fluid animation to look forward to.
I'm glad to be wrong. The dynamic poses are wonderful to look at, and the manga is just as engaging and visually beautiful in its own way.
Also, the guys are such dorks, I love them.
I mentioned this in the anime comments, but I'll repeat here too: I love how all of the characters are given characterization so you're not just cheering solely for Karasuno. It doesn't have to take much, but all of the characters are well-rounded that it hurts no matter which team loses.
Also, I'm so proud of them as they develop their skills and overcome their weaknesses.

As someone with a disability, this story resonated with me on a deeper level than expected.
Sure, I didn't get as much bullying by comparison (maybe because I live in a more accommodating environment) but I still got it. Before I learned about it, I was unsure of what I did that led to harmful responses, because I had no idea what made me so different to my peers growing up, and why it was difficult for me to learn how to fit in.
The fact that Japan is not as accommodating towards those with disabilities adds more weight to the story, and it demonstrates this in a heartbreakingly believable way. (the content of Nishimiya's letter to Ueno hit home for me)
I can understand when the parents get frustrated at having to deal with their disabled child, because I also went through some of that, including a parent denying my disability or wishing I was different.
("One day you'll wake up in the morning, and you'll just be normal." "Wow, you don't look disabled!")
But despite all that, stories like these give hope of success for these people, without it coming across as cheesy or forced. And yet it seems such a progressive story can be difficult to put out in a culture where it's okay to turn a blind eye to problems that aren't yours, and not wanting to start anything problematic.
I also like how forgiveness and redemption are addressed. There's realistic context, that karma does its job, but if someone sincerely wants to make up for their mistakes, they shouldn't deserve any more crap.
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I don't know why this story is listed as "romance" when it wasn't really there, and honestly it was something I wasn't looking for (as someone who isn't interested in romantic stuff)
It's probably implied, but I felt like this story is more than that.
It demonstrates the development of deep relationships that don't have to be always romantic in order for the message to get across.
Success doesn't have to mean getting a date-mate.
But that's just my interpretation on this story.