Timboli: It seems it may have just been an update, a good one full of extras though, as the original Hedon has now disappeared from GOG.
Its a whole new episode that is now combined with the original episode. Appears to be just as big, if not bigger than the first episode. First level took me 54 minutes, second 1 hour & 11 minutes (there are ten levels per episode).
The base price appears to have been raised a bit, completely understandable. New episode has been awesome so far. Great music, atmosphere, a LOT more action packed than original episode.
Love it... its a love letter to 90s 2.5d shooters with level design and atmosphere inspired by 'immersive sims' like Thief & Arx Fatalis.
Only complaint so far is that text was magnified and it garbles some of the longer messages. You can open the console (with tilde ` key) and see the message properly though.