I backed Spark in its Kickstarter and got a chance to read and play the finished product soon after it was released.
The game itself is well-explained and has simple, clear and well-explained rules, showing good workmanship.
While the rules may be elegant and simple, mastering Spark is not for everyone. Spark puts world- and storybuilding in the hands of everybody at the table. Only if all participants can handle that, Spark will flow well. The good news is - you learn this while you play Spark.
In Spark, at least with a prepared setting world, you begin by selecting the beliefs in the world that you want to explore as a group. Then some factions to represent these beliefs. You define some basic stats for the GM that he can roll on. And finally you create some ties between those factions. It's all in the book, the process is explained very well.
Then you define characters - by chosing your own beliefs, ties, stats and skills. Spark knows only four stats: Body, Mind, Heart and Spark. The physical, mental and emotional aptitude to influence his or her story directly, plus the Spark - the ability of the player to shape the world and story surrounding the character. Spark is a meta-gaming attribute. Inexperienced players do have problems with Spark, because the Spark attribute is intended to allow you to shape the story. Unfortunately you can also use it to nullify challenges the game master tries to create before they arise. If you're stuck in thinking "I have to protect my character at all cost" you're tempted to use your Spark attribute to prevent the GM from creating challenges. And then not much at all happens.
So, playing Spark requires players who want things to happen - including to their characters. Spark invites you to put the notion of character safety aside and make the story and the beliefs king. This supported well by the gaming mechanisms in that you can only take damage when you really want to influence things so hard that you would actually rather take harm than let one failed roll stand as it is.
Because rolls play a different role in Spark. Everybody is allowed to make declarations - you can boldly state pretty much anything and if nobody at the table objects it will become game world fact. So if you declare you make a triple salto jump over a canyon and no one - including the GM - objects, then that happens. If somebody objects, you're rolling out a conflict. You roll the needed attributes and skills your action requires, but the GM might for example roll against you and state that you fall into the canyon because it's too wide - a physical danger, so the GM would roll his physical attribute. Highest roll usually shapes the story, but there are rules for taking damage to increase the result of your roll or for escalating the roll.
Rolls then usually only happen if the people at the table have different ideas of where the story should go. Sometimes this is the GM to make the game more challenging. In principle a game without rolls would be possible. Only that usually some dynamics exist because of the various factions, beliefs and ties that put different characters, and possibly their players at odds. So, the rolls exist not to determine the fate of a player. You can narrate that perfectly fine without rolling. The rolls exist to determine the story outcome and twists.
This is a lot of freedom, and if you appreciate story-telling freedom, you will enjoy Spark. It's not something you can expect to unpack at the gaming table and to work right out of the box with most established RPG groups. It takes a bit getting used to. But if you accept the challenge that the Spark style of playing and storytelling presents, you might find it to be very rewarding.
For the would-be world creators Spark is a gem. For my own sessions I wrote a Spark / Fallout setting within less than two days and it was ready for play. The process of creating setting worlds is well-documented and fun. Highly recommended.
[4 of 5 Stars!]