A quick browsing at Steam reviews shows that people who (probably) finished it, have played around 10 hours (I've seen 9.6h lowest and 14.1h highest, ignoring the ~2h reviews.)

This guy here, who did a quick (positive) review of the game wrote that the game should take around 10h to complete (see highlighted reply in the comments:
https://www.youtube.com/watch?v=WgmodIcp77w&lc=Ugy9vihF2cVQRebZA2h4AaABAg.9W0hVs7zKV09W1T1tm8Ef9

I own the game, but haven't finished it myself. I've only had time to play a little bit so far.