Diving straight in, the work opens with a brief note about how it provides a ready-made, populated location for gamemasters to use, or useful background for players whose characters are scumborn or belong to a scum faction... and just in case you are not sure what that means, it then launches into an introduction to the whole concept. Briefly, a scum swarm is a space-faring community with a very democratic - even anarchic - approach to everything: collective decision-making, concensus... and little regard for rules or reverence to what more settled societies may find important.
From such generalities, the narrative turns to a specific group, the Stars swarm. Born out of industrial unrest in turbulent times, the swarm began with workers in lunar orbital facilities taking control of the resources around them... just when the situation back at headquarters took a turn for the worse, and so nobody was in a position to object as the collective upgraded propulsion systems and took off, gathering many other refugees as they departed. Rather more ordered than some swarms, they now follow a set route around the system, trading as they go but still adhering to their original libertarian collectivist lifestyle.
Looking at the swarm's relations with others also provides ideas for how they may feature in your game. Provided you are not in a hurry, for example, hitching a ride can be an interesting way of relocating to a different habitat or planet. Some habitats send those they don't want around any more to the swarm in a form of exile. The swarm does the same in reverse, dropping off those unable to conform to their particular way of doing things. There are plenty of examples of specific collectives and individual ship crews for you to select one whose interaction with your characters should prove interesting. As for characters wanting to have background or history with the swarm, there's plenty for them as well. Most of what is here is what would be regarded as 'common knowledge' - or at least what you could acquire with minimal research - so there should be no difficulty allowing players access to this work.
Next comes descriptions of some of the actual vessels that comprise the physical swarm, sufficient for any interaction or character visits you may have in mind. This is followed by a selection of NPCs to populate the vessels, or act as representatives of the swarm wherever your characters meet them.
Finally, if what has come before hasn't already given you plenty of ideas, a selection of plot hooks is presented to help you interweave the Stars swarm into what is going on in your campaign.
Overall, this adds an extra, fascinating element to the already rich tapestry of life in this setting. If you are happy with a lot of adaptation, you could retool the swarm to provide a really unusual encounter for any other spacefaring game that you play.
[5 of 5 Stars!]