Geared towards a younger YA audience, the story does a good job of covering a wide variety of topics ranging from practical questions like how the kids will address their father to how they deal with a broad range of emotions (confusion, anger, grief, joy, etc.) that each of the family members experience. What truly makes the book shine is that it never gets preachy or teachy, but manages nonetheless to bring up a plethora of important issues while doing so in an entertaining way.
Like many British YA novels, the book assumes a level of innocence that you wouldn't find in an American treatment of this topic, but that actually serves the story well in this case as the adults are actively supportive and responsible. As difficult as the changes may be for all, no one expects the children to deal with matters on their own.