One ladder could simply be books by Bartoletti. If I include THE BOY WHO DARED, I can take a running leap into a side ladder of Holocaust fiction.
Another ladder could be books about hate groups such as skinheads, klan, and a more contemporary party who shall remain nameless here so as not to be inundated with complaints about my politics (since that takes the focus from ladders BUT I did just receive a nonfiction book about it to review and have a tough time psyching myself to read it right now). Side trip ladders could be books about bullies and bullying and in interesting leap from there could be to Teddy Roosevelt, bully for him!
Yet another ladder can focus on this time period immediately after the Civil War: Reconstruction, which takes us into historical fiction.
Books about those who educate at the risk of their own lives, who defend those others would subjugate is another possible ladder.
Too many ladders and not enough time or energy to climb them all.
Someone on Twitter posted a link to cool bookshelves. Here is one such cool one.