But according to Disney, that book doesn't exist in the Universe, right?
(though I get what you are saying)
Right, but if you are casually browsing
amazon and see the book for 4 bucks....you might miss the fact that it is the legends book and not the movie's novelization.
Just an aside, after reading Catalyst and then Rogue One: A Star Wars Story, I decided to run through the entirety of the official Star Wars canon.
(my reference is the canon listed on Wookieepedia).
http://starwars.wikia.com/wiki/Timeline_of_canon_media
Here it lists all forms of media (books, movies, comics, video games, tv, promos)
I'm not into video games and comics, so those I'll skip.
So far I'm up to watching the Prequel Trilogy again. I did read the PT book, even though it is considered Legend (non canon). Those books made the PT much more enjoyable. Yes its the same story but I liked it better.
By the time I make to Catalyst again (doubtful if I will re-read it), Rogue One should be available to buy