Sounds interesting, but it appears to be quite commercially successful? Is it still reasonably horrifying? I've come to expect at least a certain level of shock and horror from Korean films.
For more context,
Along with the Gods: The Last 49 Days is the sequel to
Along with the Gods: The Two Worlds. The plot is a direct continuation of the first one, but functions on its own as its own self-contained story which is imo the absolute perfect state of a sequel. If you're going to watch just one of the two, watch the Last 49 Days.
The Two Worlds is a competent execution of a great concept,
The Last 49 Days however is a flawless execution of a great concept with a fantastic plot & character development. Both are definitely more in line with Korean drama than a Korean horror, though I'd say they're both in the epic genre more than anything - bit like a Korean version of Dante's divine comedy.
Without spoiling everything which makes The Last 49 Days so good (I highly recommend not reading the plot synopsis if you intend to watch it):
-The setting is just wonderful. It jumps between rundown Korean council apartments about to be demolitioned into the various zones of hell, which look appropriately like hell.
-Thematically it is all about betrayal, penitence, forgiveness, murder and injustice - yet the tone is a surprising mix of serious moments and bloody dark, bloody good comedy which I did not at all expect.
-Rather than a horror film, I would compare the franchise to any film about extraordinary legal battles. If you ignored the gnarly visuals of burning souls trying to climb atop a pillar to escape the flames or a gigantic soul devouring carp covered in screaming faces it'd be really easy to see this as an Ace Attorney series.
-The plot and character development is tremendously well-structured, easily the strongest thing about the Last 49 Days. The film runs three narratives together; one is in the present day living world, one is in the present day afterlife, and one is in the past. All three of them fit together like a puzzle.
I wouldn't disregard it because of its commercial success,
Korean films with harrowing filial piety redemption stories occasionally break the box office there. And they do it so well!