You don't have time for niceties, so you opt to grab the entire case.

Knowing you have little time to waste, you try lifting the case right away. The case is somehow even heavier than it looked! Gritting your teeth, you lift as hard as you can - only then getting it to budge! As you carefully lift the case, you glance across the room back at the harpy; she's meticulously filing each book into the shelves around her, and even rearranging some of the ones already there. She is too focused on being a neat freak to notice you stealing off with the most valuable book in the room!

You creep towards the large exit doors, painfully aware of how exposed you are with your hands full. Even though the walk to the door realistically took just a few seconds, it felt like hours! But by some miracle, you make it out of the library with the book in your possession. As you leave, you hear the clattering of another stack of books hitting the floor- it seems like you should have plenty of time before the book's absence is noticed.