Even if they manage to get a cancel mob on you, it's pretty well known that those fizzle out if the target doesn't give them more ammunition by acknowledging them. So, if it gets bad and you handle it well it's just a temporary setback.

Cancel mobs get off on having influence over the target's emotions. Deny them that and they lose their fuel.

I recommend looking at some of SunnyV2's dissections on influencers who have been cancelled or ruined their reputations some other way: https://www.youtube.com/@SunnyV2/videos

The main rule for surviving is pretty prominent in the thumbnails themselves: never respond.

Since your book doesn't have anything to do with the attackers then that complicates things. In that case you might have to straight up market the book with ads and such, and try to get review-ignorant readers. The attackers will lose energy after some time, so those bad reviews could get buried by genuine readers.

You should probably consult with a PR specialist really.