Yesterday (25th October 2018) Alan Wake returned to Steam just in time for Halloween.
To celebrate this, Remedy has also slashed the price of it by 80%, selling at £2.28/$3.00. What's better is that the entire franchise is currently selling at 80% off, which means it includes Alan Wake's American Nightmare also.
Currently the game is only available digitally on Steam but Remedy have stated the game will return to other digital stores soon. The reason why Alan Wake was removed from digital stores in the first place was due to licensing issues of some of the songs found in the game.
To buy Alan Wake on Steam, click here: https://store.steampowered.com/app/108710/Alan_Wake/