This work (which comes as a landscape format PDF, which doesn't work well on screen - except perhaps on a tablet - and even worse if printed out) begins by explaining the 2d20 'Momentum' system that is used for this game. Ideally you need to purchase a special d6 marked with special symbols to use as a Combat Die, but as you probably won't have one, there's a quick chart to enable the use of an ordinary d6 instead. It then explains that each character is described by six attributes: Cunning, Daring, Empathy, Might, Passion and Reason. There are brief descriptions of each, along with notes on how they are used in Attribute Tests, rolled whenever a character undertakes an action with an uncertain outcome. To make an Attribute Test, pick two attributes that make sense for the situation which give you a target number and roll 2d20. Each die that rolls equal to or under the target number scores one success, and each die that scores equal to or less than the character's weaker Attribute scores two successes. The Narrator (GM) assigns a Difficulty to the task, which determines how many successes in the Attribute Test are required for the character to accomplish whatever they wanted to do. Brief examples and advice on setting Difficulty are provided, and Complications and Momentum - the game mechanic from which the system gets its name, are explained.

You gain Momentum every time you score more successes than you actually require. These extra successes can be used to make your action even more mind-blowingly epic, or saved up to bolster a later roll by adding extra d20s. If two characters are operating in opposition to each other, it's called an Opposed Test, and they both have to not only succeed in the Attribute Test, but get more successes than the other character to win out. If you are looking to increase your chances of success, as well as adding bonus dice through Momentum, you can call on your Luck - each point of luck gives you a success. Teamwork and assistance from other players can also help. The whole idea of Momentum is that one success often leads to another, and fits well with the heroic protagonist like John Carter of Mars... but there is another side to the coin, Threat. This works for the Narrator in a similar manner, with all their NPCs sharing a pool of Threat that begins equal to the amount of Luck the PCs have, and fluctuates during play in the same way as each individual PC's Momentum does. Characters can do other things with Luck as well as boost their die rolls, and gain them by doing noteworthy things during a game. The discussion then moves on to Action Scenes and how they are played out. It's a turn-based system, with each character (and NPC) acting in turn until all have had a go. PCs normally go first unless the Narrator uses a Threat point to have an NPC go first - but unusually, there's no 'initiative', the players get to choose who goes first, and each player decides who acts after them! There are many things that can be done in a turn, which are explained here; along with the results of combat such as taking damage... how to recover from damage is also explained. OK, now you know enough to have a go at the playtest adventure.

Pregenerated characters are provided for a short but dramatic adventure in which the party - including John Carter and Dejah Thoris themselves - on a diplomatic errand to the kingdom of Vonika which wishes to enter into an alliance with Helium. There's an opportunity for role-play as the party settles down and gets to know each others - there are suggestions for various pastimes, and notes on how to adjudicate them - and then the peace of the trip is rudely disturbed by another flier attempting to ram the party's craft! It doesn't matter who wins the ensuing fight, both outcomes are catered for, and in any case, the remaining fliers will need repairs before continuing on their way, and this will not be as straightforward as you might think.

As an adventure it is very much an exerpt, but it brings over the flavour of the game well, and introduces the Momentum system if you've not played it before. It's a great way to discover if this game is for you and your group... and if it is, the core rulebook and other materials await!