Volume 4 contains chapters 31 to 40 plus bonus pages (fan art!) and translations notes. As I have stated in the previous volume reviews. This is rated T+ for ages 16+.
Sayonara, Zetsubou-Sensei revolves around a teacher called Zetsubou-Sensei (real name Nozomu Itoshiki) and his class of unique students. Zetsubou-Sensei is one of the most depressed people you will ever read about. All he wants to do is die. His strange personality is somehow attractive to the females in his class such as a super positive girl, a hikikomori, a stalker, a foreigner, a quite girl, a perfectionist, a girl with a tail fetish, an illegal immigrant and more! Every single character (apart from the ordinary girl who says she isn't ordinary) is really strange! Basically, this manga is about a class full of strange people who talk about everyday things but delve deeper into the truth and make them seem really odd/bad/funny.
New Years cards, Birthday parties, Christmas, Spring cleaning, Exams, Setsubun (Feb 3rd), Valentines Day. Nozomu Itoshiki sure is busy in this volume!
With 18 pages of translation notes at the back, I kind of feel sorry for the translator. I don't think Koji Kumeta realised that his book would one day be translated into English.
For those with japanese culture knowledge, this may be one of the funniest things you'll ever read! For those without, I think you'll still find it funny although it may be a bit difficult to understand.