Right off the bat, the concept is nothing new. There are System Apocalypse books and books where the MC is entertainment for aliens.
The MC Carl doesn’t really have anything too special about him. No special race, class, stats, items, quests or patrons. However, he does have a special companion, his cat Princess Donut. She is quite powerful for their level and quite an advantage. I also find her quite annoying. Her character does develop over time, but even by the end of the book, she’s still annoying sometimes. I hope that improves. The book does lack in a few LitRPG aspects, but promises to improve in the sequel.