There was a time when gamers were forced to go to a store and spend anywhere from $20 or $60 on a new video game. These were all large games that took many hours to complete, but few people were actually completing them.
You'd play half way through the game and either get bored or a new game comes out that steals your attention. So you end up with a library of games that are nearly or almost completed. When current generation consoles came out, they offered a brand new way of gaming. You could download smaller games from the Internet for a much less price.
Gamers could now spend $8 on game that has understandable poorer graphics, but can be completed in a much shorter amount of time. The Walking Dead game series is part of a new breed of downloadable game where players can have the feeling of a short game, but actually have a long game. The games come in episodes and each episode has a beginning, middle and end, but also a continuing storyline.
You only have to spend $5 and you can have an gaming experience without the long term commitment or disappointing graphics. The developers equate it to a night at the movies. You spend money on tickets and have a nice evening of fun and nothing more.
The Walking Dead series has become very popular and is a stellar mix of storytelling and action. It doesn't hurt that it's based on a massively popular television show, but I can see this episodic gaming becoming very popular. Imagine American Horror Story episodic game, I think that would blow your mind.