The Walking Dead episodes have done the business for Telltale, totalling more than 8.5 million sales.

There being five episodes inflates the number of actual people playing somewhat, and there being varying platforms and prices means calculating a sum of money earned is hard.

On Steam the entire season costs £21, although it's half-price at £10.49 today - quick!

The Walking Dead.

On Xbox Live Marketplace the first episode is free and all others are 400 MSP (£3.40). On the App Store the first episode is free, all others £3 and the entire season £10.49. On the PlayStation Store episodes are £4 and the entire season £16.

Telltale boss Dan Connors told the Wall Street Journal that each customer spent, on average, $16.

The WSJ averaged it out at $5 per episode to calculate more than $40 million earned. That's fantastic, and it also means a second gaming series of The Walking Dead is a Sure Thing.

Said Connors: "We also have The Walking Dead signed up for another season, so we're gonna use a lot of the revenue we're generating to continue to grow the company."

Connors said in a separate interview with Red Bull that Telltale was looking at how to carry saved games over from the first series of The Walking Dead into the second.

The Walking Dead has been available for months and months. It's a post-apocalyptic survival game about managing strained relationships. It also happens to feature zombies.

There's a Walking Dead TV series that takes its cues from the original source, the comic, but Telltale's game tells its own tale. And The Walking Dead is probably Telltale's best work.

Oli Welsh reviewed the entire series for Eurogamer back in November, and The Walking Dead went on to become one of our Games of 2012.