Yes, Blizzard has for most of the life of WoW, put an abundant amount of lore in the books published outside of the game. However, I never had a hard time to follow along with the amount of the story that the game itself provides without the books.
I don’t mind that WoW doesn’t have 30-minute-long movies in it, just to explain 30 minutes of game play lore. Like some other MMO’s.
People who are discontent with the game will complain about everything the story in the game and the story outside of the game in the books because 1 they themselves couldn’t write and be published if their life depended on it. 2 they couldn’t run or even work for a gaming company because their total lack of ability to even manage handing out burgers at McDonnalds.