This book, by Osamu Dazai, is an example of the Japanese genre of shishosetsu, a kind of autobiographical fiction. It's different from what we think of as autobiography, in that the purpose is not so much to tell a story - there is no real emplotment, beginning, middle, end in the traditional (or Aristotelian) sense, but rather, the text is a sort of rambling exploration of the self. Style is de-prioritized, sincerity and immediacy are tantamount. There is no constrained form, but rather, an attempt to establish a direct link between author and reader, to explain a particular perspective.
The book is largely autobiographical, based on events from Dazai's own life. He was a literary rock star, but a deeply miserable guy, attempting suicide several times before finally succeeding. There's actually a monument at the spot where he killed himself (along with his mistress), and apparently people gather there on the anniversary of his death every year.
In any case, the book itself is interesting. It makes me want to learn Japanese, for starters, because no matter how great the translator, there's no getting around the fact that the grammatical structure of Japanese is completely different from that of English, most importantly, for this book perhaps, in that it is entirely possible, and even common, to construct a sentence in Japanese with no subject. Apparently the entire book is written in this form, which would be particularly appropriate to the work itself. Though I wonder if the Japanese reader would really think of this as particularly artful, given that it's apparently a standard thing to them. But I guess that's a question for psycho-linguists to answer.
The book is the related story of a very unhappy guy who is essentially chronicling his downward spiral. Though it's hard to say if it's really a downward spiral - though he does pinpoint a moment at which he ceased to be human, it's not entirely clear that he was ever really human (by his own definition) to begin with. One question is what it means, in his eyes, to be human.
There is a clear parallel to Notes from the Underground (Dazai was big into Dostoevsky, and the main character refers to Crime and Punishment), in that both are notes from deeply unhappy men who are convinced of their own uniqueness, but there are definitely differences. Dostoevsky's character is raging against rationality, and the way in which it dehumanizes people, so in a sense, though he calls himself a mouse, etc, he could be seen as claiming that he is really the only human. Dazai's character, Yozo, sees himself as inhuman, mainly, it seems, because he lacks certain basic human traits. He claims, for instance, that he has never felt hungry. However, there is also a certain issue of domination at play - he is unable to say no to anyone, to turn down anything. In this sense, one could say that he is entirely determined by the outside world. Despite the fact that he has an inner life, he keeps it hidden from the outside world. In fact, his behavior is entirely, he claims, an act, he "plays the clown" for the amusement of others, refusing to let his own feelings show.
But I'm not certain if this is really the case. For instance, he wants to be an artist, and actually disobeys his father in order to pursue his artistic career, and confesses to the other authority figure in his life, Flatfish, that he wants to make art. So it seems as though the masking process is incomplete in this case, and at times he does behave authentically. I wonder if the same could be said for the Underground Man? I think that it's slightly different in his case, in that the construction of the Underground Man is such that he can't behave authentically, because he has no stable self. Yozo, on the other hand, certainly has an inner life, it's just a rather empty one. He doesn't seem to have any real will of his own, or rather, the will that he does have is purely towards self-destruction - he can get booze and drugs, and drink himself into a stupor, without any difficulties. But then again, he also seems to have a brief lull of happiness, directly following his marriage. But even there, it's hard to say if he's happy. Maybe it's most accurate to say that he is so constructed as to be incapable of happiness?
There's more thinking to be done here.