In wich order do I read this series?

Meino_Weeaboo said:
The original is the vocaloid song serie. Then we have the novel, which is an adaptation that gives waaaay more details about how and when everything happens. Then we have the manga, which is a different take on the story. The first 18 chapters are the same as the first 2 volumes of the novels, but after that, things take a dark twist. I really recommend you read the novel first because nothing would make sense if you read the manga before the novel. The manga is great, but only if you understand the original story. THEN... we have the anime titled mekakucity actors. I guess you COULD watch it, but i don't recommend it. It's, once again, a different take on the story, except it's a pretty meh one. It's not that bad, but it doesn't do the vocaloid series, novels, or manga justice.

TL;DR:
Vocaloid series --> Novel (which is a detailed adaptation) --> Manga (Which is a different take on the story) --> Anime (but i don't recommend it because it's pretty meh compared to the others.)

Have fun :P