I think that one example of "difficult and disturbing content" would be the manner in which Sade and Femi see their mother gunned down. It is difficult to process because of the savage manner in which she is killed and the political machinations that motivate her death. For the children to be the ones who discover the body is difficult to process. Adding to this would be how this act represents the exposition of the work, something that jars the reader in the most initial of stages.
Another example of "difficult and disturbing content" would be how the children have to fend for themselves in London. It is not a narrative where the standard read of children persevering and triumphing is evident. Rather, it is one filled with abandonment and isolation. In a setting in which so many children are left unattended and discarded, Sade and Femi find themselves in the same predicament. This can be seen as difficult and disturbing for readers to comprehend in terms of being able to empathize with characters placed in the most challenging and horrific of conditions.
The traditional notion of justice is also something that is inverted in the novel. It is one reality in which political discord happens amongst adults. Yet, to see this visited on children, the most innocent of victims, is something that could also be seen as disturbing and difficult. The political threats, the need to hide, and the fact that childhood is essentially robbed from them because of political notions of the good could be construed as disturbing and difficult. The death of innocence at the hands of political opportunists is always disturbing and difficult to comprehend.