The idea that a death of a parent can be kept secret starts to become core to the story. As a result of being orphaned the children start to fall apart leaving food to go off and their routine to fall apart.
The battle for supremacy continues between the eldest children but the disintegration of the family unit, which comes together briefly when the mother is buried in concrete in the cellar, soon drifts apart again.
It is hard to like the main voice, Jack, not just because he is a loner but because he seems to deliberately set himself apart from the world. As a piece of fiction that gives a description of a 15 year old attitude it is accurate.
What should be interesting is the pattern the family fall into once the school holidays end and the grief has started to ease.