In my first month of novel reading, it was quite enjoyable as a story. The face-slapping aspect provided a satisfying entry point into the genre, but eventually, it lost its appeal. I found the plot engaging, and I didn't find the nationalism overly problematic; it was just part of the narrative. Some readers might be more sensitive to those themes, but for me, it wasn't a deal-breaker.
Around chapter 680, the nationalism became less prominent, giving way to a fresh storyline. Around chapter 705, the harem elements started to shine, so if that's not your preference, it might be best to stop earlier. I read it consistently without skipping chapters, even though there were both highs and lows. To me, it was a decent read, though perhaps my mind filtered out the less interesting parts.
In summary, if you're looking for a top-notch novel, this isn't it. I picked it up because my other options weren't updating, and while the face-slapping moments had their moments, the MC's actions sometimes left me questioning. The system served mainly as a tool for temporary power-ups, which the protagonist tried not to rely on but still used sparingly. Nationalism wasn't a major issue for me, as long as it didn't cross a certain threshold.
If you can accept its flaws and view it as a light-hearted, over-the-top read, then maybe give it a try. Otherwise, there are better options out there.