This thread is for the Monogatari Series in general. There are two thread's for Nekomonogatari (Black) and Monogatari Series: Second Season. But I think it is better to make one general one, than to make one for every new one that comes out.
Story Sypnosis from Baka-Tsuki:
"The Monogatari series centers on Koyomi Araragi, a third year high school student who is almost human again after briefly becoming a vampire. One day, a classmate named Hitagi Senjōgahara, who infamously never talks to anyone, falls down the stairs into Koyomi's arms. He discovers that Hitagi weighs next to nothing, in defiance of physics. Despite being threatened by her, Koyomi offers his help, and introduces her to Meme Oshino, a middle-aged homeless man who helped him stop being a vampire."