Porn Mags are training items that can be found in a wide variety of locations around the Village. They are used to increase the players maximum lust score - it costs 50 experience points and one night training to increase maximum lust by one point.
The Porn Mag will be given a random title and issue number in the description detailing the players "training". The title is a combination of two phrases picked from two different lists, each list containing 52 possibilities, giving a wide range of outcomes from the mundane to the amusing to the ridiculous.
The player character, as is his wont, throws the magazines onto the fire at the end of a training session, making them a consumable item. There is technically a finite amount of porn mags on the island, but they are in such abundance that it is unlikely that this would ever become an issue.
Prior to build 0.101, porn mags would increase lust by two points. The gain main have been reduced out of balance concerns, or possibly printed porn just isn't what it used to be.