Liberty's Daughter by Naomi Kritzer.
Sadly the rich were not eaten
Beck Garrison lives on the seastead, the classic libertarian dream of a sovereign nation in the middle of the ocean. If one ever made it further than the 'buying a cruise ship' phase. In Beck's universe they made it quite a bit further than that, and the book's strongest point is building out what these seasteads would look like.
A few different 'nations' have sprung up on the converted cruise liners and sea platforms, from the debauchery of New Amsterdam to the unrestrained techno-capitilism of Sal...