The main narrative tension driving this game is a quest to free your titular vagrant twin from cryo sleep after they've been abducted by some unsavory types. The task is simple but the road is arduous as you then proceed to earn enough credits to free your twin, exploring a vast and varied intergalactic environment in the process. It's both the elemental story -- rescue your family from malevolent forces -- and the enormous scope of the world in which this story is set that give this game the feel of a sci-fi epic poem.
As is the case for many epic poems, the structure of Superluminal is episodic and the rhythm is that of a melodious and mnemonic repetition. The player character traverses numerous worlds (several dozen in my case and likely more left unexplored!), interacting with a diverse cast of characters coming from a wide range of socioeconomic situations and cultural backgrounds to buy, sell, and trade your way up to the requisite 500k credits. Each world to visit is evocatively described in just a scant few words and, similarly, every character is brought to life with a terse, smartly composed description. Truly, reading the description of each new planet brought me such great joy -- to take one example, at random, "slender megastructures rise gleaming from the silvery continents below, arcing over oceans" -- and I was heartened to re-encounter familiar descriptions as I revisited planets, akin to a Homeric bard repeating "wine-dark sea" for the umpteenth time.
The game itself is also very compelling. There's a bit of a puzzle trying to match the odds and ends that you're able to buy off inhabitants on one planet to the needs and wants of inhabitants on other scattered planets. Each of these matches is something of a hyper-episode in the larger story. The pared down mechanics (certain verbs common to IF games are stripped out, and there were no instances that I ran into of needing to play 'guess the verb' to advance) make the game easy to jump into, even for a newcomer to the genre, while the variety of ways to earn credits keeps the game interesting. The main quest can be completed relatively quickly (Spoiler - click to show)as there's a large but fairly easy job that will earn the player character sufficient credits to free their twin, but this is only a small portion of the joy of this game. As with many epics, the pleasure is not in summarizing the main story line but luxuriating in the encyclopedic details of a fully-realized world. This is a poetically charged reference book -- the highest compliment coming from someone who adores reference works!
Superluminal achieves one of the finest balancing acts between the literary and game elements that make the best interactive fiction so compelling. This is an epic poem that you are play as well as read.