Outside of the material in the FFG books themselves, do folks have any Star Wars books they recommend using for reference? I read Wookiepedia a lot, but frequently the information can be pretty minimal and awkwardly written.

My Top Five:

The Jedi Path - this is an in universe force handbook, written for students at the Jedi temple. It is an incredible treasure trove of information and a great "artifact" to give to the player of a force sensitive player. It is also the first book in a set of four (so far). The other three are all excellent, but none are quite as good as the Jedi Path. The others are the Book of Sith (the Emperor's collection of Sith writings from throughout history), the Bounty Hunter's Code (actually two books bound together - the handbook for the Bounty Hunter's Guild and a Mandalorian Death Watch manifesto), and the Imperial Handbook (a field guild to the Imperial Military). All of these books are highly recommended.

The Essential Atlas - The best single volume on the Star Wars universe. In addition to the individual planetary write-ups, it has a lot of great history on galactic geopolitics. Basically, like Wookieepedia, but official, well edited, and in one convenient volume for quick reference at the table. Plus, the one page descriptions are good for showing to players at the table when they ask "What does my character know about Taanab?" or "What is common knowledge about Ithor?" It gives a reasonable amount of info without going down the internet rabbit hole. Also, it lists all the other planets and moons in systems with a significant planet, which can be very helpful for adventure planning. This is my favorite book of the various "Essential Guides" though most of them are fantastic.

Complete Vehicles - This is a collection of all the Incredible Cross-Sections books. It's got teardowns for just about every vehicle and starship seen on the screen during any of the six films. It's great if you need to show everyone exactly how the inside of an AT-AT is laid out or to get a general sense of where certain facilities on a Nebulon-B are. Plus, the in-depth diagrams for under-the-hood stuff on a landspeeder or an X-Wing could be really interesting for technician type characters.

The Wildlife of Star Wars: A Field Guide - It looks like an almanac-type biological field journal of various creatures, beasts, and monsters throughout the Star Wars universe. It is beautifully illustrated and has lots of helpful anatomical and habit information. It was written and illustrated by the biologist who designed most of the alien animals and creatures for Episode I. It was published between Episodes I and II, so it lacks the arena monsters from Attack of the Clone and anything else made after Episode I, but it has plenty of emphasis on the original trilogy stuff like Tauntauns, Banthas, and Dewbacks (and Wampas... and Rancors... etc).

Millennium Falcon: Owner's Workshop Manual - This is a Haynes manual for a YT-1300 freighter. If your group ended up with the Krayt Fang from the EotE box set, or some other YT-1300, this is the definitive guide to that ship. It's a fun book written like a shop manual and has a catalogue of factory options, common modifications, and history on the model. It's also got schematics and enough technical explanation to make your mechanics sound knowledgeable. There is also a Haynes manual available for the Death Star, but I haven't picked it up yet - I imagine it will be equally fun, but perhaps a bit less useful for RPG purposes.

Obviously, I cheated a bit on the Top 5 thing by including other books within a given series under a single item, but I'm happy with the list. All of these are helpful books that I've gotten a lot of use out of.

For Age of Rebellion the Essential Guide to Warfare The Imperial Handbook, and the old WEG Rebel Alliance and Imperial sourcebooks are definitely on my go to list.

Imperial handbook and Bounty Hunters Code.

The Jedi and sith books of the same type aren't very helpful to me, since there are no jedi or sith in my campaigns.

EDIT: Thanks for the tip on the YT-1300 owners manual thingy, I just ordered it

Pretty much anything with handy maps or pictures I can use as examples.

Second the Imperial and Alliance Sourcebooks from WEG there's also a Game master's sourcebook that I picked up a couple of years ago that goes over adventure building although I bet I got the name wrong!

You can't got wrong with Star Wars Blue Prints and the Rebel edition.

My Top Five:

Thanks for the comprehensive answer! It's very helpful!

All of the old WEG d6 SWRPG books are great. This site has tons of their material http://d6holocron.com/

Those books pretty much created the Expanded Universe. Most of the stuff is pretty easy to convert from d6 to EoTE.

As far as novels go, if you're looking for flavor - the Han Solo trilogy book 'Rebel Dawn' gives a good example of a fringe character leaning towards rebellion.

Otherwise, the Timothy Zahn novel 'Choices of One' does a great job displaying the difficulty of Rebel cells - infiltration, making strange bedfellows and unpalatable alliances, and betrayal at every turn.

Beyond that, unfortunately, most of the Rebellion era books were real early in the publishing scheme. So things like 'Splinter of the Mind's Eye' show that time, but can be difficult to make it through compared to later, more polished books.