Just finished this very fine novel, Catalyst: A Rogue One Novel, by Star Wars veteran James Luceno (2016). I rate this as one of the best Star Wars books of recent times.
A great read, in my opinion. A nice dose of science and math flavor. Some interesting tidbits about life during the chaotic last days of Republic, through end of Clone Wars and transitioning into Empire. Interesting in that Darth Vader and Palpatine are mentioned, but never "seen", on camera. We do spend some time with Tarkin and Mas Amedda. We get to know scientist extraordinaire, Galen Erso. We also come to know Commander Krennic, a bureaucrat in charge of a certain space station's superlaser project.
A nice tie-in to elements of the prequels. A calm-before-the-storm type novel without much action to speak of, but with plenty of groundwork laid for connecting this story into the upcoming movie, the original trilogy, and the prequels (without mentioning Jar Jar). I like it. I like this time period on the cusp of the Galactic Civil War. Some beings are already forming into a nascent resistance, here and there. More will follow.