There isn’t much, but some further info does exist its just REALLY tricky to find, scattered across a bunch of books and requires a bit of deductive reasoning, it also helps to dig into other sources of Infinity Lore.
As mentioned in the core book (pg 146) Boosters are “paired” systems, essentially giant rings of a Mass Driver floating in various orbits, 1 ring points towards a destination, another in the opposite direction. They also mention these things are in little clusters sitting near planets or wormholes so I assume you’d find these things pointing all different directions in planetary orbits and on popular orbital-transits multiple Boosters firing in the same direction.
That same section also mentions that 1 Booster can throw you towards another Booster, which basically means that the idea of these things works like the “Space Highways” from Cowboy bebop. Booster rings are seeded en masse throughout a system and you travel down them gaining a whole bunch of DeltaV.
All of that can be implied from the pg146 reference.
We also learn here, but in other references that Circulars “stop” at Vila Boosters especially clusters in a Local system but don’t make use of them. despite the terms used by Circulars they really are just vessels for transiting Wormholes and not specifically in-system travel which smaller vessels can do more economically. Page 161 also mentions many Caravanserai are located near Vila Booster platforms so you can take info from the Haqqislam book on those.
Other info is scattered throughout the core book and the supplements is mostly in regards to locations where you can find Boosters, but more or less any inhabited world or large industrial location will have at least 1 and according to the info on pg 292 individual Boosters can also be re-targeted as needed.
Page 146 of the GMG also has a bunch of info on Vila Boosters and the summary of WE’RE NOT ALONE IN THE NIGHT (GMG, pg 81) mentions that the types of people you find staffing Circulars are similar to those on Vila Boosters, so the adventure “Circular File” as some good analogies to draw from.
In the Aleph source book (pg 8) we learn that Vila Boosters are also responsible form transmitting data to/from locations and between systems.
Now, in terms of physical description rather than capabilities, Infinity within ts own sources seems to contradict itself. Some references say the Boosters are a series of rings that boost-boost-boost then decelerate etc like a system spanning mag-lev tunnel others seem to describe them more like a limited version. Think giant space-ship sized coilgun that gives you an enormous initial shove followed by a lot of coasting.
Personally I prefer the former version as it works better for acceleration in space that doesn’t need inertial dampers… a series of 0.1g pushes a hundred times is healthy than a single 10g push. And a nigh-post scarcity world Booster rings seeding systems feels very Human Sphere to me and space-highways make space-pirates work as a concept.
Finally there is this piece of art http://i.imgur.com/50mptl4.jpg the 2 pieces in the top right is the Wotan Jump gate between Paradiso and Svalarheima. While it isn’t a Villa Booster per se it should give you an idea of the design of space-based objects in the Human Sphere, you can also see some ships and base designs in the rest of the picture which should help you come up with a cool visual to describe to your players.
In terms of setting a Adventure on a Booster… I’m not sure that the Boosters themselves are a place that would see much foot traffic outside of the crew. From all the descriptions it seems more like the Vila Booster mechanisms are located in the same region as other space stations/caravanserai. And that those stations themselves are where you see most traffic… caravanserai are fairly well described in the Haqqislam book. I could see a Booster being a short shuttle ride from such stations but if they are giant magnetic accelerators having them too close to humans would be… bad. Still I am sure they have minor (heavily shielded) facilities for crew/maintenance etc.
I hope that all helps… I spent a lot of time trying to track down any specific art of a Villa Booster, some people I spoke to said there should be one piece out there, but I couldn’t find anything. Hopefully with the Spaceship book from Modiphius we can get a picture of these devices.