Just took a look and I think it's the full game - file size is the same as GOG, who sells all three episodes in one download.
According to the Deluxe Edition page, it would appear that this is what makes it a Deluxe edition:
Soundtrack
Story book (plenty of background info and artworks)
“Making of” booklet
Papercraft mask of The Raven (printable)
Digital poster (printable)