Will the book be available in audio format?
Books tends to fill gaps between (or before) what we see in-game, but are not necessary to make sense of what we experience in-game.
I think the Garrosh stuff between MoP and WoD is the only real exception, and they had a short story on the website for the quick and dirty version of it. Which is still a poor way of handling that transition, but still. That’s the only one I can think of that felt like you were supposed to do external reading to know what’s going on.