Finally read it. It was… good!
! To be honest, I don't think it really deserves the absurd fame it got. It is a good battle shonen manga, but I honestly don't see it being above average in any aspect. For how short it was, I think its quality also dwindled for a while - but once it got back it got back for good. The anime was definitely the reason behind this tremendous success and then the buzz effect kept it going - I read the manga, but I kept checking on the fights and key moments to see how it ended up animated and the anime really is that good (and that soundtrack!).
! Talking about what I think the author did particularly well: first, the comedy. Unlike most shonen manga that start heavy on the comedy aspect and loses it more and more as it advances, mistaking high stakes with angst, this one kept the comedy on the first arcs as present as in the last ones and always pretty good.
Second, the threat level. I was fully expecting the Moon demons to go the same way as Bleach's Espadas and after the first went down, suddenly all of them would start being defeated on 1x1 fights, serving only as hype tools for the Captains Pillars. But no, all the way to the end the Upper Moons remained absurd threats to the point that not a single one was defeated on a 1x1, all of them requiring at least a bit of external help to be defeated (most requiring an entire squad) - well, there was that guy from Zen'itsu training, but he doesn't count.
! Sort of still on the "threat" aspect, I think it is worth singling out that damn final arc. This is what a final arc in a shonen has to be! God damn it. The fucking stakes, the tense atmosphere… there wasn't a single moment you felt like the good guys had a safe moment (again, Zen'itsu's fight aside). Even if you knew the good side had to win in the end, the author actually managed to make things unsafe the whole time. And the last fight, despite being endless, never faltered. I started listening to the OST while reading those chapters and, boy, it was perfection.
! Leaving the excitement over the last arc and an almost perfect ending aside (that the author had to ruin with that final fanfiction chapter... but I am trying to erase that from my memory), the rest of the manga was... well... mediocre.
! Gotouge deserves a compliment for trying to invest time on each character and not allow a single one to go to waste. Still, at times you could see it was a conscious effort. Things like Gen'ya's complete change of attitude over the most menial talk with Tanjiro, or Giyuu's forced drama that was also resolved in a single chapter after another menial talk... those reeked of "afterthought".
That leads to another less positive aspect, it being Tanjiro being the epitome of every main character trope. From the absolute necessity of having every character have their lives changed by him, to his initial (and actually endearing) portrayal as a high empathetic character being thrown out the window just so he could become the 1000th angry main character screaming the enemy name in a rage fit and getting 100 power-ups by force of can't-forgive-youuu power... He started as a character that had something to say and ended up as just another main character with nothing unique about them. When he started screaming at Hantengu he would pursue him to hell if needed to rip his head off (even though Hantengu did nothing to warrant some sort of personal grudge out of him), I could tell the character was dead.
On that note, though, gotta commend Gotouge for not going the obvious way and having Tenjiro be a descendant of Yoriichi, but instead come from a line of nobodies. There was a certain disconnection in the way Yoriichi ended and how Tanjiro line was just a family of friends, it kinda betrayed all we are used to see... but it was a very pleasant disconnection.
! Main character aside, the side cast was quite interesting and managed to hold their ground through their entire thing.
Zen'itsu and Inosuke are KnY Ishida/Chad. And just like those, they fade into the background as soon as the Captains Pillars appeared. The difference is that, here, it was a shame that it went that way because those two are so. damn. entertaining. Specially Inosuke. I don't think there is one single moment I got tired of their presence (even though during the Red Light District I couldn't really understand what was the point of insisting on Zen'itsu sleeping shtick), every second with them was gold.
The support case like Haganezuka and Gotou too were some of the best parts in the entire thing (I'll never forgive Gotouge for the completely unnecessary urge to turn Haganezuka into a bishonen).
! The Pillars are more of a mixed bunch. I think this was one of the aspects that suffered from Gotouge apparently not having the mid-sections of the manga planned ahead, some Pillars apparently never found their place in the manga and had to be forced somewhere. Mitsuri… the poor thing. Giyuu too, as I said, despite his connection with Tanjiro, seemed very empty. To be honest, I think Shinobu is the only one I really like in the group (she actually being my favorite character), but I can admit that all the others had their merits as characters even if they don't really fit my personal taste, so it was always interesting to follow them.
! The villains... well, villains are always my favorite part, in 90% of the shonen I read my favorite character is always a villain at least in their first appearance. Here, despite Gotouge giving every villain a backstory and having all of them being amazing threatening enemies, I really didn't thought any of them had actual substance to be fully realized characters, except Akaza and Kokushibo.
Btw, if Kaigaku was the new 6th and Nakime was the new 4th... who was the new 5th? Did they just hid during the final arc?
Muzan was pretty disappointing. After he emerged from the coccoon he kinda became interesting, but it was too late for that after 80% of the manga being just an Aizen wannabe.
! Plot wise, like I mentioned when talking about the Pillars, I think it was very sloppy. For such a short manga, you would expect things to be more tight, but there are many aspects that seem underdeveloped. Like that "mark training" that didn't go absolutely nowhere (so the characters got this mark that would get them a boost in fight but those boosts never actually mattered, just like the "shortening life span" they brought never mattered - it never does -, or the supposed connection with "demons crest" - the similarities were mentioned when Mitsuri awakened hers, but then entirely forgotten). Or Yoriichi's dool being used as some tease about the hanafuda slayer past but it just never appearing in the flashbacks. And there are a lot of other things that make me think everything between the Train Arc and the Final Arc was an afterthought.
! The fights. Honestly, with the exception of Zen'itsu's single move and Nezuko basic fighting style, I couldn't understand one single movement any character used (the Hantengu fight being one noteworthy exception). Most of the time that wasn't a problem because the fights were very concise in the first arcs. And by the final arc, when the fights got longer, things had already improved in a way it didn't really mattered. Probably the only time I felt the fight became a drag and couldn't wait for it to just end was during Red Light District Arc (to be fair, I don't think I liked anything in that arc).
So, yeah, fun. Entertaining. But average. I love that a manga managed to shake the monolithic dominance of OP, but I would be happier if reading it I had felt it was truly deserving of my praise (besides that final arc).