It was the fourth in the series Dungeon Crawler Carl. The basic premise of the series is that many, many years ago -- like primitive humans in our timeline -- aliens made contact with Earth and made a deal. And given our evolution at that time, the humans did not understand the deal. Now the aliens have come to collect, which means scraping Earth for its resources.
So us Earthlings are given an option to enter a dungeon, which is livestreamed to an intergalactic audience (think Battle Royale or The Running Man or Hunger Games), and if you get to the 18th floor of the dungeon, you get your planet back. Of course, in all the planets aliens have done this to, no one has ever made it past floor 12...
If you like video games, it's super fun. Like there are achievements and loot boxes and what are effectively YouTubers making running commentary. It kind of reminds me of, like, James Bond and those sort of stories, where the question isn't really "is Carl going to survive this book" but "what dangers will Carl face and how cool will he look while he manages to get out of this situation?!"