Reddit reviews Star Wars Imperial Sourcebook, 2nd Edition (Star Wars RPG)

That edition is infamous for inaccuracies and contradictions, it's the edition handed out to civilian-facing positions, and was heavily redacted due to the high probability of it being leaked or intercepted.

You can get a much more accurate and comprehensive edition here. Although this edition is a bit outdated, hence its availability on the civilian market, it'll still get you a much better picture of Imperial structure and operations generally.

The whole Age of Rebellion Line (Careers/Specs are pretty era/faction agnostic), Imperial Duty Chart, and maybe the WEG Imperial Book.

Of course if you wish to follow the new Canon: Aftermath Trilogy, Bloodlines, Marvels Shattered Empire and of course watch/play the upcoming EA Battlefront II campaign.

The old West End Games d6 system had two great source books.

The Death Star Technical Companion has a lot of interesting floorplans, and according to that, things like the Death Stars and Star Destroyers were basically built using the same modular rooms. They're not ready to use battlemaps or anything, but I remember there being a good deal of great layouts for things like crew living areas, detention center, etc.

http://www.amazon.com/Star-Wars-Death-Technical-Companion/dp/0874311209/ref=sr_1_1?ie=UTF8&qid=1452105488&sr=8-1&keywords=death+star+companion

There's also The Imperial Source book from WEG. I don't remember if there are a lot of deck/floor plans in it, but there is a TON of information on the Imperial military is organized.

http://www.amazon.com/Star-Wars-Imperial-Sourcebook-2nd/dp/0874312108/ref=sr_1_1?ie=UTF8&qid=1452105642&sr=8-1&keywords=west+ends+games+imperial

Obviously, neither will have compatible stat blocks for the new system, but if you can find paper backs of either for <$10, I'd say they were essential if your game is going to have a lot of Imperial Entanglements, and you want a solid source you can pull from without having to invent it all on the fly... which is also certainly an option!

The D6 SWRPG played a huge role in my childhood- so much that even when I finally got rid of all of my legends novels, I kept my collection of SWRPG sourcebooks. It's pretty heavy in original trilogy and legends material, and completely lacking in anything from the prequel era (West End Games lost their license about the same time Episode 1 came out). For an RPG set in the classic trilogy, though, you can't go wrong with the D6 system.

Even though the books are all out of print, they can be found on Amazon for relatively cheap. All you need to get started playing is the core rulebook, although I strongly recommend investing also in the Trilogy Sourcebook, the Imperial Sourcebook, and the Rebel Alliance Sourcebook, as the supplemental material will help you to more easily round out the setting.

Fragments from the Rim is a good resource if you want some ideas about how to incorporate more fringe elements (unsavory types like criminals, bounty hunters, and pirates) into your gameplay.

If you've got a player who wants to roleplay a Jedi character, the Tales of the Jedi Sourcebook has a lot of supplemental material for roleplaying force-sensitive characters (including rules for every force power introduced into the SWRPG canon). It's not essential- there are rules for using the Force in the core rulebook, but this supplemental material may be useful.

The Gamemaster Screen is also super helpful. If you're new to running RPG games in general, the Gamemaster Handbook has a lot of good "how to" information about facilitating interesting and enjoyable play sessions as a Gamemaster.