I'm really looking forward to tackling this in my "The Force of Star Wars: Examining the Epic" course next semester. I'm expecting some great discussions with my undergrads!
I highly recommend reading the novel Catalyst by James Luceno, which is essentially the prequel to the film and directly relevant to its plot, and also the Rogue One novelization by Alexander Freed. I've quoted some of my favorite passages from the novelization that shed new light on the story here.
I also recommend the Visual Guide. My favorite revelation from the book is (mild spoilers!) that the red sash worn by both Lyra Erso and Chirrut Îmwe is known as the Red Sash of the Enlightened, marking them both as related to the Jedha sects of the Church of the Force -- not Jedi, but believers and protectors of Force knowledge in the galaxy. That fits neatly with what we already know of both characters, but I like the visual symbolism.
Last, Rebel Force Radio's brand new episode of the Star Wars Oxygen series, which explores the scores of Star Wars with music professional David W. Collins, begins an eye-opening (ear-opening?) analysis of the Rogue One score. Terrific stuff.