The Mysterious Stranger by: Mark Twain
The last book Mark Twain wrote.
In 1590 a few boys are living happy sheltered lives in a remote Austrian village named Eseldorf. The story is narrated by one of the boys—Theodor, the village organist's son—in a first-person narrative. One day, a handsome teenage boy named Satan appears in the village. He explains that he is an angel and the nephew of the fallen angel Satan. Young Satan performs several magical feats. He claims to be able to foresee the future and informs the group of unfortunate events that will soon befall those they care about. The boys don't believe Satan's claims until one of his predictions comes true. Satan proceeds to describe further tragedies that will befall their friends. The boys beg Satan to intercede. Satan agrees, but operates under the technical definition of mercy.
My favorite book too!
They made a small clip of it in this clay movie its disturbing.
https://www.youtube.com/watch?v=fBGGAjMg9vw