With the return of Voldemort, it further solidified her need to know about the world she could potentially be thrust into if Harry failed. History was almost never kind, and Hermione felt that if Voldemort wanted to return to the days of Pureblood supremacy, surely she must know what she was up against. There was hundreds of years worth of history, documenting everything from Pureblood traditions, to the slaughter and exile of magical creatures.