"Kirigirisu", by Dazai Osamu. His writing never disappoints me, I find that I can always relate to the things he wrote despite them being decades old. My favorite story in this collection is "Chikukendan", which starts with "I am confident that I will someday be bitten to death by a dog", something that I can totally relate to. Most other stories in this collection are not as cheerful, but all very relevant and definitely worth reading.
Previous (2012-08-22): "Year Zero" by Rob Reid
Next (2012-10-17): "The Call of Cthulhu and other Weird Stories" by H.P. Lovecraft