She'd been deep undercover for the better part of a year now and it had occurred to her only a few months into the job that there was no way she could realistically store all of the information she gathered by simply committing it to memory. As it was, memory was a fickle and deceitful thing. Better to store information in the form of writing. Hermione added a few key words and phrases she either learned or thought required some research, then placed the parchment back in the book and returned the book to its original place.