It’s now pretty well known that West End Games’ take on Star Wars became a major seed of what became the Expanded Universe. Whilst additional stories of questionable canonicity have always been part of the franchise – Alan Dean Foster did Splinter of the Mind’s Eye back when the original trilogy was coming out, based on the story George Lucas had mapped out for the second movie in case the studios wouldn’t give him the budget for Empire Strikes Back – but it’s fair to say that the whole Expanded Universe thing didn’t kick into high gear until Timothy Zahn’s Thrawn trilogy, and it’s well known how when he was writing that Lucasfilm gave him a fat stack of West End supplements to use as background reference material. Although much of the Expanded Universe has been declared non-canon by Disney (though they still acknowledge its existence under the Star Wars Legends label), extensive details of the West End line remain having crept into canon via the later films and other materials that didn’t get made into unhistory.
One reason that the West End line has been so influential is because of the sheer mass of material produced for it. As well as providing sourcebooks based on obvious subjects like the Rebellion and the Empire, it also did supplements based on specific releases, so not only did you have supplements focused on each of the original trilogy but you also had a phenomenon where each new Expanded Universe hit ended up getting its own West End sourcebook building on what it did, and since that Expanded Universe stuff was building on things West End had done you ended up with a feedback loop going where West End were constantly churning out ideas. (This was exacerbated in their late-life shovelware period, where they cranked out Star Wars stuff at a wild pace because it was a licence to print money for them and the main thing making their business viable.)
Just as West End was the wellspring of the Expanded Universe, The Star Wars Sourcebook is the seed of that approach. The actual 1st edition Star Wars RPG rulebook didn’t actually include an awful lot in the way of setting information, and to be honest it didn’t necessarily need to – if there’s one franchise out there where you can reasonably be sure most people have a passing familiarity with the setting, it’s Star Wars. The Sourcebook was published alongside the core rules and was mainly authored by Bill Slavicsek, the line editor for the Star Wars RPG, and you can sort of see it as the other half of the originally intended core line. (Remember, the supplement churn didn’t go into high gear until the RPG started selling in a big way.)
I don’t usually judge books by their cover here, but just scroll up a second and have another look at that cover: compared to the action-packed shot on the cover of the core book, it’s really kind of dull – someone printing off polaroids on a computer system. That’s appropriate – not because this book is inherently boring, but because it’s constructed as a reference work – and had the game flopped, it may have well been the only reference work in the series. It’s essentially a dense stack of both stats and explanations for all the sorts of stuff which they expected would come up a lot in a Star Wars game, bearing in mind that this came out at a time when you had just the original movies and absolutely no pre-existing Star Wars RPGs to set anyone’s expectations.
As a result, it’s interesting to see what they chose to include here and what they left out. There’s a long section on how starships actually work – it’s what the book leads off with, in fact – which is incongruous these days because you’d expect the first major section in a more recent Star Wars setting guide to either cover the history of the Republic and the Empire and whatever the hell it is which is going on with their successor states in the new trilogy era, or maybe an exploration of the Force given how Force-centric Star Wars has become. But in those heady pre-Phantom Menace days of 1987, in the time before Knights of the Old Republic became a cornerstone of fan appreciation, the history of the galaxy just wasn’t that important. What you mostly thought about when you thought Star Wars was scruffy technology, cool aliens and robots, Stormtroopers, spaceships, and the iconic characters. The Force was undeniably important, but at the same time it was important as an enigmatic quirk of some of the characters, not as a pervasive cultural touchstone of the setting.
Basically, if something appeared on the screen during the original trilogy, you can probably find a writeup of it here. It’s not absolutely encyclopedic – there’s no detail on Hutts, for instance, though that may be because it wasn’t canonically clarified whether “the Hutt” was Jabba’s title or his species, and you don’t quite get a breakdown of every single alien species you can spot in the cantina scene – but you’ve got a surprising amount of stuff crammed in here. The NPC writeups and other time period-dependent materials are provided with the assumption that your campaign is going to take place in the (admittedly quite extensive) downtime between Star Wars and The Empire Strikes Back, which is reasonable enough, though personally I would go for between Empire and Return of the Jedi, since that’s a time period where most of the major players from the movies are either frozen in carbonite or undertaking a long and difficult search to track down where Han Solo’s carbonite coffin is stashed, giving you ample opportunity for the players to step up and deal with major crises.
The absence of some things are quite surprising. For one thing, there’s no details on how the Empire actually functions beyond the writeup of organisation of Imperial Stormtroopers, which would seem to make it hard to play some iconic character types (how am I supposed to play a smuggler without some idea of what’s contraband and who can be bribed to look the other way before the Stormtroopers show up?). For another thing, there’s no “atlas” section or other writeups of any of the planets that appear in the saga, though admittedly since those are all defined by a single terrain type it’s arguably unnecessary.
You can get really deep into the West End Star Wars rabbithole if you elect to; the member of my Monday evening group who’s running Star Wars in his GMing slot has a fat stack of their supplements and that allows him to pull out all sorts of odd bits and pieces to spice things up. But if what you’re after from a Star Wars RPG isn’t novelty so much as the familiar trappings of the movies, The Star Wars Sourcebook gives you more or less all you need; it and the original Star Wars core rulebook between them would be a very complete offering just by themselves.