I just finished re-reading the first volume and the main thrust is pretty straightforward. We meet Sung Jin-Woo, who's the absolute weakest hunter in a world where monsters pour out of gates and only hunters with special powers can fight them. The plot kicks off when his entire low-rank party gets wiped out in a suspiciously difficult dungeon, and he's left for dead. Instead of dying, he gets access to a mysterious System only he can see, which turns his life into a kind of brutal RPG. The first book is essentially his transformation from being everyone's punching bag to someone who can actually fight back, but it's a grueling process. The System forces him to complete daily quests that are literally torture, like running for hours until he collapses.
What I find most compelling isn't the power-up fantasy itself, but the atmosphere of constant dread and isolation it builds. Jin-Woo is utterly alone with this interface; nobody else can see it or understand what's happening to him. The story spends a lot of time inside his head as he grapples with the sheer absurdity and horror of his situation. The book ends with him stepping into a transformed version of that fateful dungeon alone, ready to test his new abilities, which sets up the notorious 'solo leveling' loop perfectly. It's less about epic battles at this stage and more about the psychological groundwork of becoming something other than human.