LOLITA by Vladimir Nabokov
It's written from the perspective of a middle aged man named Humbert Humbert, who falls in love (and even gets sexually involved) with a 12 year old girl named Dolores.
So yeah, he is pretty much a pedophile, however the novel itself is actually cleverly written and quite enjoyable, even with all the controversy surrounding the topic and characters. The term "Lolita", is meant to describe a sexually precocious young (or prepubescent) girl. There have been two movie adaptions of the book and the film "American Beauty" was inspired by this novel. Even the name of protagonist Lester Burnham is an anagram of "Humbert learns".
THE DIVINE COMEDY by Dante Alighieri
Its an extremely long poem that was originally written in Italian, but its also renowned as being one of the greatest works of world literature. The poem is divided into three parts, Inferno, Purgatorio, and Paradiso, and it is meant to describe Dante's (the authors) journey through Hell, Purgatory and Heaven, as he is led by his guide, the Roman poet, Vergil. The book has been refered to by games aswell, such as "Dante's Inferno" (duh), the Devil May Cry series, Bayonetta, Final Fantasy: IV, V, VI, Castlevania: Aria of Sorrow and Castlevania: Dawn of Sorrow, Tamashii no Mon, The Last Remnent, Fallout 3, and Persona 3 just to name a few. (There are obviously many more)