End Of Series Depression. The feeling you get when you've just finished a really good series. Originally coined for the feeling after watching an anime series, hence series, it however is far from limited to this. It is also often experienced after finishing books, films, video games, almost anything with an interesting story and characters in fact.
It doesn't even have to been the end of the series; it could be the end of the latest in a series when the next item is some time away.
Many attempts have been made to stave it off including taking as long as possible to watch a series, or as little time as possible. But none is known to have worked. The best known cure seems to be to try and get stuck into something else, although this isn't fool proof and often just delays the EOSD.
I've just finished the new Harry Potter book; it's given me really bad EOSD.