Halloween is behind us but the sale is still on. You have until 10 am Pacific time to get all Croteam titles at discounted prices.
The Talos Principle is 40% off and Road to Gehenna is 33% off.
Also, Sam titles are up to 90% off.
http://store.steampowered.com/search/?snr=1_4_4__12&term=Croteam