Cheapest ever price on IsThereAnyDeal for The Talos Principle at ~$19.26 AUD ($13.59 USD)!
Metacritic score of 85, very favourable reviews
Update: further 50% off with Alienware Arena coupon - ~$9.63 AUD!
Alienware are giving away 50% coupons which stack with current Steam sale, making the game ~$10 AUD! Thanks to user bobjane (I assumed these coupons had run out but there's still ~1271 as of 10PM 11/11).
The DLC is 66% off too, I've been waiting for that to go on sale since it came out. Thanks OP! This is absolutely my favourite game from last year and I've been looking forward to playing more of it.