Amazing book just like all other's written by Jodi Picoult. I love that Jodi does not take sides - she throws the reader into the arena, gives arguments for all sides and makes you work out where you stand by yourself. And it's ok to sit on the fence. She takes the most difficult subjects and lays down the details and you walk away feeling enriched and enlightened. 
Thankfully we don't experience school shootings in the UK/Europe so much. We have knife crime so I can see why we have such strict laws on shot guns. This book really opens your eyes and makes you wonder how well you really know your own children. How often do you check their phone/computer/gaming console. What protection do you have in place to shield them from the bad world - should we shield them from everything. 
I felt so sorry for Peter - yes, we know he is guilty right from the start and no, I have never had to experience the sort of bullying he did, but I have children, I went to school and I have feelings - I can imagine how one would feel to be treated their whole life the way he was. It shows the spiraling effect actions of other have on the whole community. 
I love Jodi's brilliance and I will never stop reading her books - they should made mandatory in schools not banned.