It's great to see Barsoom come to life in the wonderful art and entertaining adventure contained in this quickstart. The rules are quite clear (if the organization is occasionally difficult for me, some concepts mentioned in advance of their presentation in the book, this seems to be somewhat common in RPG rulesets but I'm still new to RPGs and it's a little confusing to me), the attributes are quite thematic to the source material as are the damage types and afflictions.
Some seasoned RPG players may find the simplified 2d20 ruleset (called Momentum too simple for their taste, but it works fine for me (and Modiphius will be publishing a conversion to the full 2d20 system as well).
The included scenario, Flags of Mars, looks fun and really fits the setting (Modiphius is working with the Burroughs Estate on this so it's officially licensed), but I'd like it to have been a little longer (it seems like it would play in 2 hours or so with a LOT of roleplaying or new players, but otherwise possibly quite a bit faster). You could easily map out a few more scenes and let the players run with the adventure (it's rather open-ended), but you'll be off the rails and out of the quickstart.
The pregens are the heroes of A Princess of Mars Dejah Thoris, John Carter, Tars Tarkas, Kantos Kan, and Sola and seem reasonably balanced and offer a variety of options and approaches to the players.
No rules for character creation, etc. just the basic system and adventure but all in all a good package (and being free it's really hard to complain).