The Question and Answer section for Extremely Loud and Incredibly Close is a great resource to ask questions, find answers, and discuss the novel.
Oskar's quest is to discover the meaning of the word "black' and a use or lock to fit the mysterious key. His purpose is to forge a bond with his father.... one last experience.
This quote expresses Oskar's disappointment with life.... his pessimism. Oskar's loss of his father, also robs him of his childhood innocence. Oskar no longer sees beauty in the world, all he sees is the darkness of his depression.