To be fair, it's not just any library - it's the Hall of the All-Knowing, the library of the gods. (Admit it, you'd like to have access to it, too.)
She's there at the urging of the hammer Mjolnir, which has been behaving oddly - and exhibiting intelligence.
So she looks for answers, and finds some (though not all, of course). It's a mystery that stretches back into the history of Asgard and battles decided by the power of Odin.
The story by Jason Aaron is that most dreaded of creatures - a retcon - but it's not terribly intrusive and mostly sticks to corners that have been untouched (though it seems to ignore stories that depicted Odin using Mjolnir in battle - when Thor was just a boy).
The art chores are divided between Russell Dauterman and Frazer Irving, as they divide the modern-day story from the historic action. It's strong, vibrant work all around.
This series continues to be surprising and entertaining - but I do miss the real Thor, and it's frustrating that we still don't know what caused him to be "unworthy." Perhaps his promised new series will clue us in.