Valve uses every opportunity to organize a Steam sale, and Halloween was an excuse as good as any. It's interesting to note that Valve doesn't announce this beforehand, and they rely on taking the community by surprise. There were some rumors that a new sale was about to go down, and gamers know that such holidays are usually accompanied by price cuts.
We can also remark that it's not a terribly attractive sale, despite the large number of games that are available. Most of the big titles only carry price cuts like 30%, which is not a lot when the full price of the game is $60 (€60). I'm sure that among so many titles people will find something to buy, but it also feels like a wasted opportunity for Steam.
Black Friday is right around the corner
Another major sale is approaching fast, and it's possible that we'll see another offering from the Gods of Valve when Black Friday comes around, but it's impossible to predict. There were some scattered Black Friday sales in the past years, the most recent one being from 2013.
Also, we shouldn't forget that there will certainly be a Winter Sale as well, so all in all, the calendar of PC gamers is pretty full.
So, what can we get for our buck? There's a nice price cut for GTA V, the Witcher 3: Wild Hunt, Shadow of Mordor, Bioshock Infinite, Left 4 Dead 2, Soma, Dying Light, and a few others. Some of you might notice that some games have nothing to do with the Halloween holidays, but this is not the point of the sale.