It’s a well-known phenomenon: the anxious, agonising self-torture writers put themselves through when releasing their second book. (Musicians suffer from a similar malady: the difficult second album.)
There are usually all sorts of worries that afflict writers upon contemplating their sophomore creation. Is it too similar to the first book? Or maybe too dissimilar? Was the debut effort a total fluke, leading to a debilitating case of imposter syndrome when trying to replicate it? What if, after momentarily basking in the publicity sun that the first one enjoyed, this second one is just ignored because you are no longer the bright new thing?