Mhm, the book was arguably required for her personal story to make sense. But mostly just for the Legion and BfA bits that Afrasiabi wrote to make her an "evil ninja 5D mastermind kekW". The Shadowlands bits? The basic premise is in the Torghast questlines. Sylvanas' makes it quite clear to Anduin that in her eyes, she is an anti-hero who does everything for the greater good in order to re-write a broken, unfair universe. And everyone else around us tells us all the time that the Jailer is a lying manipulating dude (although, in the end, he indeed did what he did for the greater good, which was something I was sure from the get go would be the ending for him - and if I got that from the basic questing, well, looks like I just did understand the story just fine?).