It's a good novel! If you like mystery and hm not really horror but I would call it psychological? Doesn't feel that 'horror' to me. There's so many twist and turn in the novel, so give it try!
To sum it.. it's not collecting ghost, but rather trying to survive and obtaining dream essence/dream solution (the one extracted from the anomalies he entered) so he can exchanged it with points to buy a wish ticket to return to his world.
The core business model of Daydream Inc. is acting as a supernatural pharmaceutical company. They dump the collected Dream Solution into the Dream Synthesizer, which acts as a crafting forge. In this world, the anomalies he entered (in novel, it translated not as anomalies but Ghost Story/Darkness) produced that dream solution/essences. To collect Dream Solution, an employee must successfully clear a Ghost Story's objective or satisfy its specific rules while holding a company-issued Dream Collector.

I've been seeing the novel everywhere but haven't read it yet because it was ongoing. Is this good? Can anybody briefly tell me what it is about? Is it a "collecting ghosts" kind of story?