The demo version on steam is the same as in here?
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No, this version features a ton more content. The Steam demo is based around the old alpha version of the game and probably only accounts for about 20% or so of the content available in the other versions of the game right now.
When the Steam EA version of the game releases it will have roughly the same amount of content to the other versions of the game, along with some premium features. You should be able to transfer your save from the Steam demo and keep playing here to experience the rest of the game so far.