Love Live! School Idol Festival is a card rhythm game based on the Love Live anime. As I mean a "card rhythm game", it's basically collect idol cards and use them as your advantage or bonus to play the game (and it also depends on their element/class you use). However the game doesn't heavily rely on the cards (from rarity or class) but mostly depends on your poking/tapping rhythm skills.
Now the nice thing about the game is pretty much collecting cute idol cards (especially if they're special or you combine them if they're the same for a better card) and build your preferred deck/team along with playing the rhythm part (plus story mode). Also anyone can get a chance to get special or at least actual decent rare cards compared to most iOS card games. So other than that, the game is pretty standard and I don't really see anything negative on the game that would bug me. It's nice overall especially with the exclusive songs.
Conclusion: Interesting anime rhythm game.
Note: Free to play and is currently available only in the Japanese App Store. Navigation/menu is not simple enough for those who don't know or not familiar with Japanese. An English version is not yet announced so far.