I would add some caution for readers in terms of some of the themes that can be sensitive, and I will include them here, which could be spoilers (so skip to below if you are concerned about spoilers). More specifically, I would warn for a girl who was raised as a boy (but may identify as a girl), pedophilia (one of the adults decides that she should marry him/that her presence is a gift for him), religious in the extreme with casting out of demons/religious figure not very pious, and stoning of others/bullying/mistreatment.
What I loved: The imagery here is fantastic. We feel the isolation, the desolation of the landscape, and the unforgiving nature of survival. The world-building in terms of the rocky island was very good. We got a very good feel for how this fowling trip was.
What left me wanting more: The book moves very slowly, and facts are often revealed slowly, making it hard to visualize the world outside of the island and understand the societal structure (though this may be presumed as it is historical/based on truth). The slow pace can make it hard to read in places, but on the other hand, this does help build the isolation and overwhelming nature of the trip.
Final verdict: Fans of LORD OF THE FLIES will enjoy this new tale of historical survival in an unforgiving environment and with evolving social structures. Would recommend for people who like compelling world-building and immersive scenarios.