Babylon's Ashes by James S. A. Corey

The crew of the Rocinante is back in the Sol system, but a group of Belters (people living in space for generations), who call themselves Free Navy, is threatening all of humanity to “save the Belt”.

Incredible space fights, piracy, ethical questions and a bit of politics make this into another amazing Expanse book. Loved it, can’t wait for the next in the series.