I must begin by emphasizing the following: this is not The Stranger. Osamu Dazai's masterpiece, No Longer Human, is often compared to Albert Camus' The Stranger, for somewhat obvious reasons: both feature disenfranchised, strange protagonists whose separation from the reality that surrounds them terrifies and haunts them. But while The Stranger is an ultimately philosophical - that is to say, detached - take on the subject, No Longer Human is a tale of human tragedy. It is firmly real; elements of autobiography flicker throughout it, tragically reified.
Told through some lost journals, it is the tale of Oba Yozo, a Japanese boy of some privilege and a descendant of a locally affluent family. Yozo, from a very young age, finds himself befuddled by the actions of human beings. Specifically, human beings in the aggregate disturb him; social interaction cripples him, and his inability to understand society forces him to take up the mantle of the jester, the buffoon, a role that, when seen historically, obtains properties of social transgression. This role continues until Takeichi, a classmate of his, points out that his buffoonery is not accidental - as Yozo wishes the world to think - but manufactured. A young Yozo grows stiff with terror; someone has seen through his facade. His interactions with Takeichi occupy a few brief pages in the short book, but they go on to frame the rest of the novel.
At the core, this is a book about depression, alienation, and trauma. Little fanfare has been made over this book's inclusion of male sexual trauma (or, really, sexual trauma in general); but it necessarily contributes to the psyche of the protagonist. And that core is what makes the book so relatable; I hesitate to claim it universally appealing, but it certainly will seem instantly familiar to anyone who has struggled with societal interaction. This relatability is tragic; it is as tragic as the ending of this book, upon which we leave the suffocating sphere of Yozo's thoughts and see him through the eyes of others. Unlike The Stranger, we see here no philosophical denunciation, correction, or indictment. This is a book of quiet devastation and unresolved pain. I cannot recommend it highly enough.