The book is called Demian: The life story of Emil Sinclair. Here's a copy paste explanation from moi:
Emil is a kid who believes in the goodness in the world. When he turns ten he realizes the world has a light and a dark side. He believes he is part of the light, and avoids the dark. He views his father and his childhood home as the ultimate power of Light. He eventually goes to boarding school (a normal thing for boys of his economic standing). A classmate named Alfons Beck brings him to bars and exposes him to the dark side, teaching him to misbehave. Emil steals an apple to impress a friend and therefore touches the dark side. He is blackmailed for his crime of stealing but Demian, an upperclassman, saves him. Demian is dark: his theology is dark, and his methods are mysterious. Emil avoids him, believing he is the dark part of himself (as everything has a dark and a light side). Emil tries to go back to the light, but is finding he cannot. He uses his teacher (a piano player) to figure out why he feels so polarized. He does not contact Demian, but finds beatrice, a painter who resembles him and shows him that he wants to be part of the light. He also slightly mentors Knauer, a student who is suicidal and begs him for answers. ANYWAYS. Eventually he rejects his teacher and finds Eva, Demian's mom. Eva represents Eve (I can explain more if you aren't familiar with the creation story from Christian and Hebrew scriptures), and her garden represents light. Emil realized he is marked with darkness, or the mark of Cain (which is the sparrow. If you saw the short films that's what that represents). The bird also represents Abraxas, a deity (aka a god. Similar to the Christian God). Emil then goes on a hunt to find Abraxas.