Important note- I haven't seen the anime. This is all based on the 61 chapters of the manga that are out right now.
I'd actually never heard of it until that point, so I felt pretty out of the loop. I decided that if two different people can feel so strongly about two different characters from the same manga/anime, then it had to be worth checking out.
So I did!
The first thing I noticed (and liked) about this manga is the art style. It's clean, it's neat, and it's really visceral. One thing to know if you're considering reading this manga is that it doesn't shy away from violence or gore. It's nothing over-the-top, but there is blood, and a few characters get limbs cut off.
It's a hectic, fast-paced manga, with a lot happening over many panels. However, the cleanliness of the art means it's easy to follow the action- it doesn't get washed out in visual noise.
The second thing I liked was the characters- each one is dynamic, with individual personality that screams off the page. Everything gets going really quickly, so characterization comes along quickly and the reader needs to keep running alongside the story to get a sense for the individual characters.
What's keeping me coming back, and will continue to do so, however, is the fact that there is a real sense of tension in the manga. In other works, you can assume that main or major characters are safe, because of their relevance to the narrative. Not the case here. It seems like no one is safe, which is refreshing in shonen manga.
I totally recommend reading this one, if you aren't already.