I personally find it very difficult to argue that any content of this book would be unsuitable for children, as I believe that the grown-up content it does contain, such as how Leslie and Jess face bullying and also the death of Leslie, represent important issues that impact and affect children all over the world. Adults would be doing children no favours by restricting their access to such material. In particular, the way in which Paterson records the reactions of Jess to Leslie's death is very accurate in terms of the emotional rollercoaster that he goes through. Consider the following quotation from Chapter 11:
Leslie--dead--girl friend--rope--broke--fell--you--you--you. The words exploded in his head like corn against the sides of the popper. God--dead--you--Leslie--dead--you. He ran until he was stumbling but he kept on, afraid to stop.
Admittedly, the very raw and painful way in which Paterson presents the emotional tumult that Jess is experiencing would be disconcerting to younger readers, and so some might argue that the very adult themes of death and the experience of grief is something that younger readers should not be exposed to. However, I believe, very strongly, that it is vital for children to be able to encounter such experiences in literature in order to equip them to face such situations when they do happen in their own lives, if they haven't already had this experience.