FastDasher: I'd imagine the crocipedia accounts for a significant portion of the file size. There's concept art and developer interviews included with it.
Unreal_Reality_2: Considering how smooth the character models look in the screenshots, there must be a TON of edges and faces on the character models. Such high poly models can take up a lot of space. Same can be true with particle effects, depending on how elaborate said particle effects are.
They are not so smooth, even if they have 50000 polygons it not takes more then 2MB. If I calculate it right and not forget something to add. Animations also don't take a much. The content which can take a lot of space are textures, videos and music. But from screenshots I don't believe that textures are in that case and if videos are made prerendered, then the size of game is mystery for me.
I wanted buy this game, but when I saw this monstrous size for that game, I refuse even to download it for free. I played much better looking games with same or less size.