Sun of Suns

A new sci-fi series with a neat premise: in the far future, these “worlds” are housed in space inside giant (several thousand kilometer diameter) balloons, and the whole world has an atmosphere, but gravity is only provided as the cities generate their own by rotating. There’s a lot more to it – I’m not gonna summarize the whole book, but if you’re in to this genre (*dan, this means you), you should read this book.