It's my pet peeve when people compare the book to Battle Royale.
Books aren't just their "concept."
And even then, Battle Royale and Hunger Games have two entirely different themes.
Battle Royale for me seemed like the preservation of innocence. Hunger Games, on the other hand, was more interested in survival, with coping, with coming to terms with the situation.
The sequels also delve into territory that Battle Royale never really tackles, such as the price of actually taking down a government, the various political machinations, etc.
Both Battle Royale and Hunger Games are valuable reads. I just think a lot of people get too attached with the elevator pitch that they don't see the important nuances and differences between the two novels.