The back cover blurb pretty much says all that you need to know: "For the first time in English, Osamu Dazai's hilariously comic (!) and deeply moving prequel to No Longer Human."
... but we'll throw these in for good measure:
"What I despise about Dazai is that he exposes precisely those things in myself that I most want to hide." – Yukio Mishima
"Dazai was an aristocratic tramp, a self-described delinquent, yet he wrote with the forbearance of a fasting scribe," – Patti Smith
Perhaps closer to a novella than a novel.
Opening line: "Welcome to Sadness. Population one."