iOS 11 taking a whopping 15.2 Gb on iPhone 7 32 Gb

I have an iPhone 7 with 32 Gb of space. I'm always fighting for space for my photos and Apple Music songs (Apple should use a better file system for musics... there's no compression). I was looking out for space killers on my phone and I noticed that the iOS 11.1.1 is taking a whopping 15.2 Gb of space. Is it normal? Does iOS need that much room? Is there a way to clean some of it?

Thanks.