Except instead of numbers, we'll use books (because numbers scare us writerly people, right?)
Book #1: To Kill A Mockingbird by Harper Lee
To Kill A Mockingbird is about a mishievous tomboy Scout and her adventures until her and her friends watch a black men getting tried in a court case after being accused, wrongly, of raping a white woman.
To Kill A Mockingbird brings to light the very large issue of racism against black people that was present in the 1930s (both the time Harper Lee grew up in and the time the book is set in) and the 1960s (the time when the book was published).
To Kill A Mockingbird has been banned or challenged at various schools for using swear words, racial slurs, and for general racism. (Just an interesting sidenote, though: it's been said that To Kill A Mockingbird is the one book other than the Bible that has changed people the most... hm....)
Book #2: Huckleberry Finn by Mark Twain
Twain uses this book to criticize and challenge the racist American society of the time and the perception of black people, specifically the view that black people weren't human and didn't have feelings.
http://swardkehoe.blogspot.com/2011/09/banned-books-week-has-begun.html (what an intelligent reader has to say about The Hunger Games)